On September 8, 2026, Artifex launched Ghostscript 10 08.0 , closing an essential load barrier overflow that the Wordfence Danger Knowledge team, using Wordfence Argus , discovered and reported sixteen days previously. It is tracked as CVE- 2026 – 39919 and lugs a CVSS score of 9 8 out of 10 A crafted PDF consisting of a JPEG 2000 photo can make Ghostscript create attacker-influenced bytes past the end of a memory barrier. We created that corruption into unauthenticated remote code implementation on a purpose-built WordPress test website.
If you run a WordPress site, there isn’t a WordPress plugin to upgrade. Ghostscript is supplied by the os or the container image, so most website proprietors will obtain the fix via their distribution or organizing supplier. Containerized websites require to be restored and redeployed from an updated base picture. We evaluated ten Linux plan atmospheres on September 15, and the official WordPress Docker image photo we checked was just one of the susceptible ones.
Key Takeaways
- Wordfence Argus found a essential CVSS 9 8 vulnerability in Ghostscript , the paper engine several web servers make use of to turn PDFs into photos.
- The fix remains in Ghostscript 10 08.0 Your operating system may include the repair to an older variation, so the full package modification matters greater than the outcome of
gs-- variation - We showed unauthenticated remote code implementation on one exact WordPress implementation. Both proof-of-concept ventures we developed specified to the Ghostscript develop they were prepared for. Our follow-up screening sustains concern concerning targeted assaults and groups of web servers that share the very same build, not a single file that works anywhere.
- This is not a WordPress-only susceptability. Any type of application that sends untrusted PDFs to an affected Ghostscript develop may be revealed, consisting of document management systems, print services, billing cpus, mail portals, and conversion APIs.
- The main WordPress Docker image picture we checked was prone. Stock WordPress does not let anonymous site visitors post PDFs to the Media Collection, so the container by itself is inadequate for an anonymous strike.
- There is no WordPress plugin to update. Set up the set system bundle, follow your vendor or host’s reactivate support, and reconstruct containers from an upgraded base photo.
- Wordfence Argus uncovered the susceptability during a WordPress 7 1 evaluation led and validated by Alex Thomas Artifex verified the record the next day and delivered the solution in Ghostscript 10 08.0.
Wait, what’s Ghostscript, and what does it relate to WordPress?
Ghostscript is a file engine. It reviews PDF and PostScript documents and transforms their pages into pictures that software application can present, print, or sneak peek. It rests beneath several applications that never mention Ghostscript by name, which is why many website owners run it without understanding they do.
WordPress does not render PDF previews itself. Considering that WordPress 4 7 , core can create a photo of a PDF’s initial page when it produces accessory metadata. On a web server using the PHP Imagick extension, WordPress calls ImageMagick , which then releases Ghostscript to provide the PDF.
The chain is WordPress, after that Imagick, then ImageMagick, after that Ghostscript Ghostscript runs as a different program, normally under the exact same account as the web server. It only begins when something asks for a photo of the PDF. A form that conserves an uploaded file to disk and not does anything else with it never ever starts Ghostscript. A form that includes the data to the Media Library can begin it when WordPress constructs a sneak peek, gave the called for software program and policy setups are in location.
This is not a vulnerability in WordPress or in the form plugin we used for testing. WordPress and the plugin were merely exactly how the data got to Ghostscript. The bug is in Ghostscript.
This is a critical CVSS 9 8 susceptability. Should I be stressed?
You ought to spot it, however the score describes a worst instance instead of a warranty.
The CVE record appoints a CVSS 3 1 rating of 9 8 and a CVSS 4.0 rating of 9 3 Those scores describe a network-facing application that accepts PDFs without a login or customer action. They explain the possible influence, not whether a specific site reveals Ghostscript or whether one PDF will antagonize its develop. Successful code implementation runs with the permissions of the account processing the PDF, which is not instantly root access.
Modern systems randomize memory areas and secure down delicate components of a program. Those securities commonly transform memory corruption right into an accident, however they do not repair the bug. On our purpose-built test web server, we still reached code execution.
We likewise examined whether one make use of works all over. We built two working proof-of-concept exploits for our laboratory develop, after that ran them 10, 240 times across 10 various other Linux package settings on 64 -little bit Intel and AMD systems: Debian, Ubuntu, Fedora, AlmaLinux, Alpine, and the main WordPress container. Neither succeeded as soon as outside the matching build, while both continued to work on that build. We after that maintained the Ghostscript executable the very same and changed typefaces, language settings, font configuration, and one core system library. The very same manipulate still done well in all four setups, although it did not prosper on every effort.
That makes the specific construct vital, but our experiment did not determine how easily an assaulter might determine it remotely or for how long adjusting a manipulate would take. A targeted aggressor might have far better info, and a hosting platform may reveal the exact same develop throughout many websites. On our purpose-built type, stopped working efforts returned a successful upload reaction while Ghostscript collapsed behind-the-scenes. Various other sites might log, block, or rate-limit duplicated uploads.
Our two files did not function unchanged across the blended bundle collection. That is solid evidence versus dealing with either documents as an universal manipulate, but it does not dismiss a different data or a collection of files gotten ready for typical builds. We did not measure plan occurrence or remote develop recognition, so we can not give a success rate throughout the Web. Site proprietors need to spot, particularly if they accept public records or run many sites from one shared photo.
What HEIF Heist informs us concerning this susceptability
Load barrier overflows are in some cases rejected as too undependable to matter on modern-day web servers. Memory randomization and various other protections do make them more challenging to make use of, and a working manipulate may require to be tailored to a specific software develop. Yet harder is not the like safe.
That is the essential link between this Ghostscript susceptability, our earlier libheif searching for , and Hacktron’s HEIF Heist research. Both Wordfence Argus findings are load buffer overruns in indigenous file-processing code that can be reached via a posted data. In both instances, our functioning code-execution manipulate relied on the target construct as opposed to working as one global payload.
HEIF Break-in shows why that restriction should not be misinterpreted for protection. Hacktron made use of AI-assisted make use of growth to turn a load barrier overflow in libheif right into trusted code implementation versus OpenAI’s Discussion forum. Its broader research study found paths to code execution or information exposure in various other real services and products, consisting of Next.js applications Hacktron reported that adapting a make use of per new company generally took one or two days, also when the group initially understood little concerning the target atmosphere. Some efforts needed countless uploaded images, but the group still got to code implementation or review information from server memory.
Our Ghostscript experiments indicate the same hazard model. Both data we developed stopped working in 10, 240 efforts throughout 10 various package atmospheres, but a build-matched exploit continued to succeed in all four arrangements that shared the precise Ghostscript executable. Attackers do not require one PDF that functions all over if they can concentrate on a well-known target or lots of web servers constructed from the exact same photo. HEIF Heist does not confirm that this exact Ghostscript problem can be adjusted in 1 or 2 days, and we have actually found no public proof that it is being manipulated today. It does reveal why the trouble of manipulating a stack overflow is not a defense and should not postpone patching.
Is my WordPress website affected?
If visitors or customers with limited consents can publish PDFs to your WordPress website, you need to presume the site is influenced up until your host confirms otherwise. This attack reaches Ghostscript when WordPress or one more tool develops a sneak peek, thumbnail, or photo from the PDF. If uploaded PDFs are just stored and never ever processed, this course is not subjected, however many site proprietors will not understand what takes place behind the scenes. Ask your hosting service provider whether uploaded PDFs reach Ghostscript. If they do, utilize the package guidance below to confirm that the solution is set up.
Set up the repaired Ghostscript package provided by your operating system or hosting carrier. Artifex taken care of the flaw in Ghostscript 10 08.0, however Linux distributions typically add the fix to the older version they currently ship. That means gs-- version may not inform you on its own whether you are covered. Ubuntu 22 04 , as an example, fixed this in package 9 55.0 ~ dfsg 1 -0 ubuntu 5 14 , which still reports Ghostscript 9 55.0. Inspect the full plan revision making use of dpkg -s ghostscript on Debian and Ubuntu, or rpm -q ghostscript on Fedora and the Red Hat family members. Install the fixed package and follow your supplier or host’s reboot assistance. For containers, reconstruct and redeploy from an upgraded base image as opposed to reactivating the old container.
Your website can be attacked in this manner just if all of these are true at once:
- A site visitor, or a person with a low-privileged account, can submit a PDF
- Something on your website then requests for a sneak peek or thumbnail of that PDF
- Your web server has Imagick, or an additional device that calls Ghostscript to make that picture
- Your mounted Ghostscript does not have the repair
Resource background puts the damaged code in Ghostscript 9 21 via 10 07 1 when the OpenJPEG decoder course exists. All 10 plan environments we evaluated consisted of that path. A variation in that array reveals that the bundle was originally affected, yet only the full package modification or your distribution’s advisory can inform you whether the repair was added later on. What each system ships adjustments gradually, so this table records the exact plans we examined on September 15:
For contrast, the final Ghostscript 10 08.0 release includes Artifex’s fix The table covers just the dated circulation and container bundles we evaluated, so the official 10 08.0 release is not consisted of.
Our test PDF collapsed Ghostscript on 9 of the 10 systems. Debian 12 made that specific documents without collapsing, but when we altered the dimensions inside the picture and attempted again, 28 of 40 of those variants collapsed it as well. A file that does not collapse your web server is not evidence that your server is risk-free.
Considering that we ran those examinations, dealt with bundles have actually shipped for numerous of these systems. Ubuntu has repaired 22 04, 24 04, and 26 04 Debian has actually taken care of 13 through its protection database, while Debian 12 stays provided as vulnerable. AlmaLinux 10 released its choose October 2
Since October 9, the official plan web pages for Fedora 44 , Towering 3 22 , and Towering 3 23 still provided the older modifications shown in our table. Check your circulation’s advisory for the precise fixed package revision.
The launch prospect for 10 08.0 additionally reports 10 08.0 and is not repaired, which is what our very own test device was running. Confirm you have the last release, or a distribution package that brings the fix.
The precise authorities WordPress Docker image snapshot we tested currently included the susceptible Ghostscript package and the software program required to reach it. It contained Ghostscript 10 05 1, the Imagick extension, and a functioning PDF sneak peek path. Supply WordPress still did not offer confidential site visitors a method to publish a PDF for preview. An opponent would require a plugin, form, application route, or account that provides that course. If you utilize the official picture, draw an upgraded base, reconstruct without relying upon a cached layer, and redeploy.
Website Wellness is only a beginning point. Under Tools → Site Health → Info → Media Handling , WordPress can show whether Imagick recognizes PDF as a layout. That does not verify ImageMagick’s policy permits PDF reviews, and it does not tell you whether Ghostscript is patched. Your host, operating system package supervisor, or container distributor is the authority on the mounted solution.
If you can not spot quickly:
- Quit accepting PDFs from site visitors and low-privileged users. This keeps those documents from getting to the converter whatsoever.
- Disable PDF reads in ImageMagick’s safety plan This likewise disables PDF sneak peeks.
- Restriction the variety of files per submission and rate limitation upload kinds. This minimizes an assailant’s opportunities, but it does not shut the vulnerability.
Relating to that last bullet point: if the initial preview effort stops working, WordPress tries once again with a various setup. If both attempts fall short, WordPress returns an image-processing error; in our form-based test, the upload itself still returned success. This retry belongs to WordPress core’s Imagick PDF loader and has been there because version 5 6, as a workaround for an old Ghostscript compatibility trouble ( Trac # 48853 We gauged one Ghostscript procedure for a safe PDF and 2 for a crashing PDF. Three attachments produced six procedures. Limiting documents per submission as a result reduces the variety of handling attempts an opponent gets in one demand, but it does not take care of the vulnerability.
Do not treat -dSAFER as a repair. Ghostscript’s sandbox restricts what a paper is permitted to do through sustained features. It does not stop memory corruption, and our screening reached the imperfection with the sandbox made it possible for.
Taken care of organizing customers can not inspect the majority of this themselves. It’s affordable to ask your host whether its Ghostscript plan includes the repair for CVE- 2026 – 39919, and whether PDFs posted by consumers get become sneak peeks anywhere on its systems. High-value sites and teams of websites constructed from a shared photo are entitled to certain interest, because numerous systems may provide the very same build to an assailant.
What this suggests for everyone else utilizing Ghostscript
Absolutely nothing about this imperfection is specific to WordPress. WordPress is one course that can provide an untrusted PDF to Ghostscript, and the very same question applies anywhere Ghostscript is used: does this software make PDFs that originated from someone else?
File management systems, print services, billing processors, preview generators, mail gateways, and conversion APIs can all do this. If any one of them send out untrusted papers to an affected Ghostscript develop, treat the update as immediate. Searching your application code for words “Ghostscript” might miss the reliance entirely, because ImageMagick or an additional library generally rests between the application and the converter.
If you can not spot every system at the same time, run file conversion in a separate, locked-down service that can not check out site secrets or connect to anything it does not need. That limits what a compromised converter can reach, yet it is not a fix.
Susceptability Recap
CVE- 2026 – 39919
9 21– 10 07 1
10 08.0
-dSAFER The CVE document states the damaged array as “prior to 10 08.0”; the at risk sub-byte tasting block was presented in 9 21 The vulnerability is fixed in Ghostscript 10 08.0. How we discovered it
We found this susceptability with Wordfence Argus , our AI-assisted security screening system, during a WordPress 7 1 security evaluation.
Argus complied with a published data past the PHP code that accepted it. For a PDF preview, that implied tracing the data via Imagick and ImageMagick into Ghostscript and the JPEG 2000 decoder below it. A visible upload trainer can verify and store a data completely well while a system program mishandles it moments later on.
The vulnerabilities that injure WordPress websites do not constantly live in WordPress itself. Several of them live a number of layers down, in software application website proprietors never ever picked by themselves, gotten to by a function as mundane as uploading a document. Protecting the platform appropriately indicates following the data all the way down. You can find out more concerning Argus in our earlier message
Our goal is to secure WordPress at every layer. That consists of searching for susceptabilities in the software program WordPress depends on, along with our Pest Bounty Program
How the insect actually works
You don’t need to understand C to follow this.
An image is a grid of examples. A grayscale image has one illumination sample for each pixel. A picture with transparency includes one more set of examples defining exactly how transparent each pixel is. JPEG 2000 telephone calls each set a part.
JPEG 2000 allows those parts differ. Parts might have different resolutions, and each example may make use of less than 8 little bits. With two-bit examples, 4 examples match a solitary byte.
A program reviewing a photo asks the system for a block of memory large enough to hold it. That block is a buffer. If the program writes more data than the buffer can hold, the additional spills right into memory past it, which may hold various other data or the program’s own accounting. That threatens, because corrupting nearby memory can transform how the program acts. If an opponent manages what obtains created, they may be able to guide the program into running code of their deciding on. This is a buffer overflow
The bug appears when Ghostscript handles those 2 JPEG 2000 functions with each other. In the minimal public examination case, a row contains 1, 024 two-bit samples. The correct jam-packed dimension is 256 bytes, and Ghostscript correctly gets 256 bytes. The loop that fills the row then composes one entire byte for each and every example as opposed to packing 4 samples into each byte. It composes 1, 024 bytes right into a 256 -byte barrier.
Think of booking 256 mailboxes due to the fact that every one holds 4 tiny letters. That suffices area for 1, 024 letters. The shipment loop neglects the four-per-box rule and places one letter in each box. After 256 letters it keeps precisely delivering, right into whatever rests beyond the mail boxes.
In Ghostscript, what rested past them was bookkeeping made use of to handle designated things. The 768 bytes that splash out on each row are derived from picture samples chosen by whoever made the data. They are constricted by the picture layout and by Ghostscript’s packing loophole, yet they can still corrupt memory addresses that Ghostscript adheres to later on while tidying up. That is just how this defect becomes greater than an accident.
Artifex’s repair adjustments the loop so it counts samples correctly and denies little bit depths that this code course does not sustain.
The 1, 029 -byte public examination file varies from a safe control data by a solitary byte, in an area defining the transparency part’s resolution. Both are valid PDFs including a legitimate JPEG 2000 photo. The hazardous problem is buried in the image’s interior geometry, so average checks of the extension, comedian kind, or basic data framework do not determine it.
Timeline
Vendor/ external action
Conclusion
Wordfence Argus located an important heap barrier overflow in Ghostscript 9 21 via 10 07 1, a number of layers under an ordinary WordPress document upload. We did not quit after making the susceptible program collision. On one precise WordPress deployment, we demonstrated that a crafted PDF might be turned into unauthenticated code execution on the server, with Ghostscript’s -dSAFER sandbox allowed.
Both proof-of-concept ventures we built did not function the same on 10 various other plan settings, so this is not one universal PDF that can endanger every susceptible server. The even more reliable risks are a targeted strike versus a recognized develop and a strike versus many sites sharing one organizing or container photo. Hacktron’s HEIF Heist study is a caution not to blunder that constraint for security: AI-assisted scientists transformed build-specific memory corruption in libheif into successful attacks versus real services. That does not establish an exploitation schedule for this Ghostscript susceptability, yet our own tests revealed that a matching manipulate continued to work throughout all four configurations that shared the exact Ghostscript executable. Build-specific exploitation is harder, not safe.
This is specifically why we built Wordfence Argus. Securing WordPress suggests looking beyond WordPress core and plugins, after that complying with untrusted information with every layer that manages it. In this case, Argus adhered to a document upload right into a system program most website owners did not recognize they were running, located a critical susceptability, and offered our researchers a course to prove what it might suggest on a functioning WordPress test website.
Whether you’re revealed relies on your Ghostscript bundle and exactly how your application takes care of records Set up the set system bundle, follow your vendor or host’s restart guidance, and rebuild container images from an updated base. If you can not upgrade yet, stop untrusted PDFs from reaching Ghostscript.
Our many thanks most likely to Ken Sharp and the Artifex group, that verified the report the day after we submitted it and shipped the fix, and the VulnCheck group for a fast CVE project.
If you know somebody running a website that accepts document uploads, please share this consultatory with them.
The post Wordfence Argus Uncovers Crucial Susceptability in Ghostscript, the Program That Transforms Uploaded PDFs into Thumbnails on Your Web server appeared initially on Wordfence
