CVE-2026-42798: Little CMS Buffer Overflow Vulnerability

CVE-2026-42798 Overview

Little CMS (lcms2) versions 2.16 through 2.18 contain an integer overflow vulnerability in the ParseCube function within cmscgats.c. This vulnerability could allow an attacker with local access to potentially cause information disclosure or denial of service conditions through specially crafted input that triggers the integer overflow condition.

Critical Impact

Integer overflow in color management library could lead to memory corruption, information disclosure, or application crashes when processing malicious color profile data.

Affected Products

• Little CMS (lcms2) 2.16
• Little CMS (lcms2) 2.17
• Little CMS (lcms2) 2.18

Discovery Timeline

• 2026-04-30 - CVE CVE-2026-42798 published to NVD
• 2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-42798

Vulnerability Analysis

This vulnerability is classified as CWE-190 (Integer Overflow or Wraparound). The flaw exists in the ParseCube function located in cmscgats.c, which is responsible for parsing color lookup table data in CGATS (Graphic Arts) format files.

Integer overflows occur when an arithmetic operation attempts to create a numeric value that is outside the range that can be represented with a given number of bits. In this case, when processing cube data within color profiles, the function fails to properly validate size parameters before performing multiplication operations, potentially leading to a smaller-than-expected buffer allocation followed by subsequent memory operations that exceed the allocated space.

Little CMS is a widely-used open-source color management library that provides color translation capabilities for applications dealing with ICC color profiles. It is commonly integrated into image processing software, print workflows, and graphics applications.

Root Cause

The root cause is inadequate integer overflow checking in the ParseCube function when handling cube dimension calculations. When processing CGATS cube data, the function performs multiplication operations on user-controlled size values without first verifying that the result will not exceed the maximum representable integer value. This can cause the computed size to wrap around to a smaller value, resulting in undersized buffer allocations.

Attack Vector

Exploitation requires local access and involves providing a specially crafted color profile or CGATS file to an application using vulnerable versions of lcms2. The attack complexity is high as it requires specific conditions to be met for successful exploitation. An attacker would need to:

1. Create a malicious CGATS or color profile file with carefully crafted cube dimension values
2. Convince a local user or application to process this file using a vulnerable lcms2 library
3. The integer overflow would occur during parsing, potentially causing memory corruption

The vulnerability does not require user interaction or special privileges, but the local attack vector limits the exposure surface.

Detection Methods for CVE-2026-42798

Indicators of Compromise

• Unexpected application crashes when processing color profile files or CGATS data
• Memory corruption errors in applications using the lcms2 library
• Abnormal memory allocation patterns in color management operations
• Unusual CGATS files with extremely large cube dimension values

Detection Strategies

• Monitor for applications loading lcms2 library versions between 2.16 and 2.18
• Implement file integrity monitoring on systems processing color profiles
• Use application crash reporting to identify potential exploitation attempts
• Deploy endpoint detection rules for anomalous color profile processing behavior

Monitoring Recommendations

• Audit systems for vulnerable lcms2 library installations using software composition analysis
• Monitor color-management-heavy applications for unexpected termination or resource exhaustion
• Review application logs for errors related to CGATS parsing or cube data processing
• Implement memory protection monitoring for applications using lcms2

How to Mitigate CVE-2026-42798

Immediate Actions Required

• Upgrade Little CMS (lcms2) to version 2.19 or later immediately
• Identify all applications and systems using vulnerable lcms2 library versions
• Restrict processing of untrusted color profile and CGATS files until patches are applied
• Monitor applications using lcms2 for unusual behavior or crashes

Patch Information

The vulnerability has been addressed in Little CMS version 2.19. The fix is available in the GitHub commit 6a686019825a89b715d16671f18d049523354176. A detailed comparison of changes between versions 2.18 and 2.19 can be reviewed in the GitHub version comparison. Additional security discussion is available on the OpenWall Security Mailing List.

Workarounds

• Limit processing of color profiles to trusted sources only until the patch is applied
• Implement input validation for CGATS files before passing to lcms2 for parsing
• Consider sandboxing or isolating applications that process untrusted color data
• Use address space layout randomization (ASLR) and other memory protection mechanisms to limit exploitation impact

# Check installed lcms2 version on Linux systems
pkg-config --modversion lcms2

# Alternative method using library directly
ldconfig -p | grep lcms2

# Update lcms2 on Debian/Ubuntu systems
sudo apt update && sudo apt install liblcms2-2 liblcms2-dev