CVE-2026-40918: GIMP PVR Image File DoS Vulnerability

CVE-2026-40918 Overview

A vulnerability has been discovered in GIMP (GNU Image Manipulation Program) that affects the PVR image file loader. Processing a specially crafted PVR image file with large dimensions can lead to a denial of service (DoS) condition. This occurs due to a stack-based buffer overflow combined with an out-of-bounds read in the PVR image loader component, causing the application to crash unexpectedly.

Critical Impact

Systems that process untrusted PVR image files are at risk of application crashes and service disruption. Attackers can exploit this vulnerability by tricking users into opening malicious PVR files.

Affected Products

• GIMP (GNU Image Manipulation Program) - versions with vulnerable PVR image loader
• Systems processing untrusted PVR image files

Discovery Timeline

• 2026-04-15 - CVE CVE-2026-40918 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2026-40918

Vulnerability Analysis

This vulnerability (CWE-131: Incorrect Calculation of Buffer Size) resides in GIMP's PVR image loader module. When processing PVR image files, the application fails to properly validate image dimension parameters before allocating stack memory. A specially crafted PVR file with excessively large dimensions triggers an incorrect buffer size calculation, leading to a stack-based buffer overflow.

The out-of-bounds read occurs when the loader attempts to process image data beyond the allocated buffer boundaries. This memory corruption results in application instability and ultimately causes GIMP to crash, creating a denial of service condition. While the current impact is limited to availability (crash/DoS), improper buffer handling in image processing code has historically been a precursor to more severe exploitation scenarios.

Root Cause

The root cause is CWE-131 (Incorrect Calculation of Buffer Size). The PVR image loader does not properly calculate the required buffer size when handling images with large or malformed dimension values. This insufficient validation allows attackers to provide dimension parameters that overflow the stack buffer allocation, leading to memory corruption when image data is subsequently processed.

Attack Vector

This is a local attack vector requiring user interaction. An attacker must craft a malicious PVR image file with specially constructed dimension parameters and convince a victim to open the file using GIMP. The attack can be delivered through various means including:

• Email attachments containing malicious PVR files
• Downloads from compromised or malicious websites
• Shared files in collaborative environments
• Automated image processing pipelines that handle untrusted input

When the victim opens or processes the crafted PVR file, GIMP's image loader attempts to allocate an incorrectly sized buffer on the stack, triggering the overflow and subsequent crash.

The vulnerability manifests in the PVR image parsing routine where dimension values are read from the file header. When these values are abnormally large, the buffer allocation calculation produces an incorrect size, and subsequent read operations exceed the allocated memory boundaries. For technical details, refer to the Red Hat CVE-2026-40918 Advisory and Red Hat Bugzilla Report #2458747.

Detection Methods for CVE-2026-40918

Indicators of Compromise

• Unexpected GIMP application crashes when opening PVR image files
• Core dumps or crash reports indicating stack buffer overflow in PVR loader components
• Presence of suspicious PVR files with unusually large dimension values in file headers
• Multiple crash events correlated with PVR file processing in system logs

Detection Strategies

• Monitor for GIMP process crashes with stack corruption signatures in crash dump analysis
• Implement file integrity monitoring to detect suspicious PVR files with malformed headers
• Deploy endpoint detection rules to identify PVR files with dimension values exceeding normal parameters
• Analyze system logs for repeated SIGSEGV or SIGABRT signals associated with GIMP processes

Monitoring Recommendations

• Enable crash reporting and centralized logging for GIMP and image processing applications
• Monitor file system activity for PVR file downloads or transfers from untrusted sources
• Implement SentinelOne endpoint protection to detect and block exploitation attempts targeting image processing vulnerabilities
• Configure alerts for repeated application crashes in image editing software across managed endpoints

How to Mitigate CVE-2026-40918

Immediate Actions Required

• Avoid opening PVR image files from untrusted or unknown sources
• Disable automatic preview of image files in file managers where possible
• Restrict PVR file processing to isolated or sandboxed environments
• Update GIMP to the latest available version once a patch is released
• Consider temporarily blocking PVR file types at email gateways and web proxies

Patch Information

A security patch addressing this vulnerability is expected from the GIMP development team. Monitor the Red Hat CVE-2026-40918 Advisory for updated patch information. Users should apply the patch immediately when it becomes available through their distribution's package manager or directly from GIMP's official channels.

Workarounds

• Avoid processing PVR files from untrusted sources until a patch is available
• Use alternative image editing software for PVR files when security is a concern
• Implement application sandboxing (e.g., Flatpak, Firejail) to contain potential crashes
• Configure system resource limits to minimize impact of memory corruption issues
• Disable or remove PVR file type associations from GIMP if PVR support is not required

# Example: Run GIMP in a sandboxed environment using Firejail
firejail --seccomp --private gimp

# Example: Configure resource limits for GIMP process
ulimit -s 8192  # Limit stack size
gimp "$IMAGE_FILE"