CVE-2026-4153: GIMP PSP File Parsing RCE Vulnerability

CVE-2026-4153 Overview

CVE-2026-4153 is a heap-based buffer overflow vulnerability in GIMP's PSP (Paint Shop Pro) file parser that enables remote code execution. This vulnerability allows remote attackers to execute arbitrary code on affected installations of GIMP. User interaction is required to exploit this vulnerability, as the target must visit a malicious page or open a malicious file.

The specific flaw exists within the parsing of PSP files. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a heap-based buffer. An attacker can leverage this vulnerability to execute code in the context of the current process.

Critical Impact

Successful exploitation allows attackers to execute arbitrary code with the privileges of the GIMP process, potentially leading to complete system compromise if the user has elevated permissions.

Affected Products

• GIMP version 3.0.8
• Earlier versions of GIMP with PSP file parsing functionality may also be affected

Discovery Timeline

• 2026-04-11 - CVE-2026-4153 published to NVD
• 2026-04-14 - Last updated in NVD database

Technical Details for CVE-2026-4153

Vulnerability Analysis

This heap-based buffer overflow vulnerability (CWE-122, CWE-787) affects GIMP's PSP file parsing functionality. The root cause is insufficient validation of user-supplied data length before copying it into a heap-allocated buffer. When a specially crafted PSP file is opened, the parser fails to properly bounds-check the data, allowing an attacker to write beyond the allocated buffer boundaries.

The vulnerability was tracked by the Zero Day Initiative as ZDI-CAN-28874 and disclosed as ZDI-26-220. The local attack vector requiring user interaction means that exploitation typically occurs through social engineering, where a victim is tricked into opening a malicious PSP file or visiting a webpage that triggers the download and opening of such a file.

Root Cause

The vulnerability stems from improper validation of the length of user-supplied data in the PSP file parsing routine. When processing PSP image files, GIMP allocates a heap buffer based on expected data sizes but fails to validate that the actual data conforms to these expected boundaries. This allows an attacker to craft a malicious PSP file with oversized or malformed data fields that overflow the allocated buffer when parsed.

Attack Vector

The attack requires user interaction where the victim opens a malicious PSP file in GIMP. Attack scenarios include:

1. Email-based attacks: Sending a malicious PSP file as an attachment, disguised as legitimate image content
2. Web-based attacks: Hosting malicious PSP files on compromised or attacker-controlled websites
3. File-sharing attacks: Distributing malicious files through file-sharing platforms or repositories

The vulnerability is exploited by crafting a PSP file that contains malformed data structures designed to trigger the buffer overflow during the parsing process. The heap-based nature of the overflow allows for sophisticated exploitation techniques that can bypass common memory protections.

For detailed technical information about the vulnerability mechanism, refer to the Zero Day Initiative Advisory ZDI-26-220 and the GIMP GitLab commit that addresses this issue.

Detection Methods for CVE-2026-4153

Indicators of Compromise

• Unexpected GIMP process crashes when opening PSP files
• GIMP process spawning child processes or network connections unexpectedly
• Memory access violations or heap corruption errors in GIMP logs
• Presence of PSP files with abnormal file sizes or structures in user directories

Detection Strategies

• Monitor for GIMP processes exhibiting unusual behavior after file open operations
• Implement endpoint detection rules for heap spray patterns associated with GIMP exploitation
• Analyze PSP files entering the environment for malformed data structures exceeding normal boundaries
• Deploy file integrity monitoring on GIMP installation directories to detect tampering

Monitoring Recommendations

• Enable enhanced logging for GIMP application events and file access patterns
• Configure endpoint protection to alert on GIMP processes with abnormal memory allocation patterns
• Monitor for PSP file downloads from untrusted sources across the network
• Implement behavioral analysis to detect post-exploitation activities following GIMP execution

How to Mitigate CVE-2026-4153

Immediate Actions Required

• Update GIMP to the latest patched version that includes the security fix
• Restrict opening of PSP files from untrusted sources until patching is complete
• Implement application whitelisting to control execution of processes spawned by GIMP
• Consider temporarily disabling or removing GIMP from systems where it is not essential

Patch Information

The GIMP development team has released a fix for this vulnerability. The patch is available in commit 98cb1371fd4e22cca75017ea3252dc32fc218712 on the GIMP GitLab repository. Users should update to the latest GIMP release that incorporates this fix.

Workarounds

• Avoid opening PSP files from untrusted or unknown sources
• Use alternative image viewing software for PSP files until GIMP is updated
• Configure file association policies to prevent automatic opening of PSP files in GIMP
• Implement network-level filtering to block PSP file downloads from suspicious domains

# Example: Block PSP file associations temporarily (Linux)
# Remove GIMP as default handler for PSP files
xdg-mime default "" image/x-psp

# Alternatively, rename or restrict access to the PSP plugin
chmod 000 /usr/lib/gimp/3.0/plug-ins/file-psp/file-psp