CVE-2026-4151: GIMP ANI File Parsing RCE Vulnerability

CVE-2026-4151 Overview

CVE-2026-4151 is an integer overflow vulnerability in GIMP's ANI file parsing functionality that allows remote attackers to execute arbitrary code on affected installations. The vulnerability exists due to improper validation of user-supplied data when processing ANI (Animated Cursor) files, leading to an integer overflow condition before a memory buffer is allocated.

User interaction is required to exploit this vulnerability—the target must either visit a malicious webpage containing a crafted ANI file or open a malicious file directly in GIMP. Successful exploitation allows an attacker to execute code in the context of the current process, potentially leading to full system compromise.

Critical Impact

Remote code execution vulnerability in GIMP's ANI file parser enables attackers to execute arbitrary code through maliciously crafted cursor files, requiring only that a user open a malicious file or visit a compromised webpage.

Affected Products

• GIMP version 3.0.8
• GIMP installations with ANI file parsing support enabled

Discovery Timeline

• 2026-04-11 - CVE-2026-4151 published to NVD
• 2026-04-14 - Last updated in NVD database

Technical Details for CVE-2026-4151

Vulnerability Analysis

The vulnerability resides in GIMP's ANI file parsing code, which handles Windows animated cursor files. When processing these files, the application fails to properly validate user-supplied data values, specifically those that determine buffer allocation sizes. This oversight creates a condition where an integer overflow can occur before the memory buffer is allocated.

Integer overflow vulnerabilities in buffer allocation routines are particularly dangerous because they can cause the application to allocate a smaller-than-expected buffer. When the application subsequently attempts to write data into this undersized buffer, it results in a heap-based buffer overflow condition. An attacker can leverage this memory corruption to overwrite adjacent heap metadata or application data, potentially gaining control of program execution flow.

The vulnerability was tracked internally by the Zero Day Initiative as ZDI-CAN-28813 and publicly disclosed as ZDI-26-218.

Root Cause

The root cause is CWE-190 (Integer Overflow or Wraparound). The ANI file parser does not perform adequate bounds checking on size values read from the file before using them in arithmetic operations for buffer allocation. When specially crafted values are provided, the multiplication or addition operations used to calculate buffer sizes can wrap around, resulting in a much smaller allocation than intended.

For example, if the parser reads width and height values from the file and calculates size = width * height * bytes_per_pixel, an attacker can provide values that cause this calculation to overflow, resulting in a small allocation that is then overflowed when actual pixel data is written.

Attack Vector

The attack requires local access and user interaction. An attacker must craft a malicious ANI file with specific field values designed to trigger the integer overflow during parsing. The attack can be delivered through multiple vectors:

1. Direct file delivery - Sending the malicious ANI file via email, messaging, or file sharing platforms
2. Web-based delivery - Hosting the malicious file on a website that the victim visits
3. Social engineering - Convincing users to open files disguised as legitimate cursor animations

When a victim opens the malicious file in GIMP, the vulnerable parsing code processes the crafted values, triggers the integer overflow, and enables code execution in the context of the GIMP process. This grants the attacker the same privileges as the user running GIMP.

The vulnerability's exploitation mechanism involves memory corruption through undersized buffer allocation. Technical details about the specific integer overflow condition and subsequent exploitation can be found in the Zero Day Initiative Advisory ZDI-26-218.

Detection Methods for CVE-2026-4151

Indicators of Compromise

• Presence of malformed ANI files with unusually large dimension or frame count values in file headers
• GIMP process crashes or unexpected memory allocation failures when processing cursor files
• Suspicious ANI files in user download directories, email attachments, or temporary folders
• Memory access violations or segmentation faults in GIMP logs during file operations

Detection Strategies

• Monitor for GIMP processes exhibiting abnormal memory allocation patterns or unexpected heap operations
• Implement file inspection rules to detect ANI files with header values that could trigger integer overflow conditions
• Deploy endpoint detection solutions capable of identifying heap corruption exploitation techniques
• Configure application crash monitoring to alert on GIMP crashes during file parsing operations

Monitoring Recommendations

• Enable crash dump collection for GIMP processes to facilitate post-incident analysis
• Monitor file system access for ANI files being opened by GIMP, particularly from untrusted sources
• Implement network monitoring to detect downloads of potentially malicious ANI files
• Configure SIEM alerts for patterns consistent with memory corruption exploitation attempts

How to Mitigate CVE-2026-4151

Immediate Actions Required

• Update GIMP to the latest patched version that includes the security fix
• Avoid opening ANI files from untrusted or unknown sources
• Consider temporarily disabling or restricting ANI file handling in GIMP if updates cannot be immediately applied
• Educate users about the risks of opening files from untrusted sources

Patch Information

GIMP has released a security patch addressing this vulnerability. The fix is available in commit 09e5459de913172fc51da3bd6b6adc533acd368e on the GNOME GitLab repository. Organizations should update to the patched version immediately.

For detailed patch information, refer to the GNOME GIMP Commit Update.

Workarounds

• Implement application whitelisting to restrict which file types can be opened by GIMP
• Use sandboxing solutions such as Flatpak or containerization to limit the impact of potential exploitation
• Configure file association policies to prevent automatic opening of ANI files
• Deploy network-level filtering to block potentially malicious ANI files from reaching endpoints

# Configuration example: Run GIMP in a restricted sandbox using Flatpak
# Install GIMP via Flatpak for improved isolation
flatpak install flathub org.gimp.GIMP

# Run GIMP with restricted filesystem access
flatpak run --filesystem=~/safe-images:ro org.gimp.GIMP

# Alternatively, use firejail for sandboxing
firejail --private --net=none gimp