Organisations Urged to Patch Pillow 13.0.0 to Block Critical Arbitrary Code Execution Flaw CVE-2026-112398
A critical flaw in Pillow versions before 13.0.0 allows arbitrary code execution via crafted files, requiring immediate updates for exposed systems.
Key points
- CVE-2026-112398 is rated Critical with a CVSS score of 9.2
- The vulnerability exists in Pillow versions prior to 13.0.0
- A fix is available in version 13.0.0
Organizations relying on the Pillow Python imaging library must update to version 13.0.0 immediately to address a critical security flaw. The vulnerability, tracked as CVE-2026-112398, carries a CVSS score of 9.2, indicating severe risk. It allows attackers to execute arbitrary code on systems that process untrusted image files using the library.
How it unfolded
- Researchers identified a heap corruption issue in Pillow’s FlashPix JPEG-tile decoder
- The flaw allows decoded scanlines to write beyond the allocated tile buffer
- A patch was released in version 13.0.0 to resolve the issue
Who is affected
The vulnerability impacts all versions of Pillow prior to 13.0.0. According to the National Vulnerability Database record, the issue stems from weaknesses classified as CWE-122 and CWE-787. Specifically, the FlashPix JPEG decoding process selects raw mode LA with two bytes per pixel. However, an unrecognized JPEG mode can be decoded as JCS_UNKNOWN with four components. This mismatch causes the ImagingJpegDecode function to write four-component scanlines into a two-byte tile buffer, leading to heap memory corruption.
Our take on the response
The availability of a fix in version 13.0.0 provides a clear remediation path for administrators. The severity rating of 9.2 underscores the urgency of deployment, particularly for systems handling external inputs. That suggests teams should prioritize updating any service that accepts user-uploaded images or generates thumbnails from untrusted sources. The specific mechanism involving OLE2 FlashPix files highlights the need for strict input validation alongside patching.
Who needs to act first
Teams should prioritize updating systems that directly accept untrusted image files from users or external partners. Check whether your application uses the optional olefile dependency, as this increases exposure. Roll out the update to version 13.0.0 in stages, starting with internet-facing services. Test the update in a non-production environment first to ensure compatibility with existing workflows. Back up current configurations before applying changes. Monitor logs for any unusual activity related to image processing during the transition period.
What to do and how to stay safe: Pillow
- Update Pillow to version 13.0.0 or later on all affected systems
- Review applications for use of the optional olefile dependency
- Validate that all input files are from trusted sources
- Monitor system logs for signs of memory corruption or unexpected behavior
Step-by-step guide: Vulnerability Prioritization: How to Rank Risks Without Wasting Time
General security guidance from the Patch Observer newsroom. It is not confirmed advice from the organisations named in this story.
Frequently asked questions
What is the CVSS score for CVE-2026-112398?
The CVSS score is 9.2, which is rated as Critical.
Which versions of Pillow are vulnerable?
All versions of Pillow prior to 13.0.0 are affected by this vulnerability.
Is there a fix available for this issue?
Yes, the issue is fixed in version 13.0.0 of Pillow.
