CVE-2026-112901: CWE-1333: Inefficient Regular Expression Complexity in python-pillow Pillow
Description
A regular-expression denial of service (ReDoS) vulnerability exists in the XBM header parser of the Python Pillow imaging library prior to version 13.0.0. The vulnerability occurs in the XbmImageFile._open function, where a crafted XBM file triggers a backtracking regular expression on attacker-controlled input, causing significant processing delays and denial of service. This issue has been fixed in Pillow version 13.0.0.
CVSS v4.0
Score 6.9medium
Affected software
python-pillow
Pillow
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Pillow Python imaging library versions before 13.0.0 contain a vulnerability in the XBM header parser (XbmImageFile._open). When Image.open() is called on a maliciously crafted XBM file, the XbmImagePlugin applies a backtracking regular expression to attacker-controlled header data before accepting image dimensions. This causes the process to stall for minutes, resulting in a denial of service condition. The vulnerability is identified as CWE-1333 (Inefficient Regular Expression Complexity) and has a CVSS 4.0 base score of 6.9 (medium severity). The issue is resolved in Pillow 13.0.0.
Potential Impact
An attacker can cause a denial of service by supplying a specially crafted XBM image file that triggers excessive backtracking in a regular expression during image parsing. This stalls the processing thread for an extended period, effectively denying service to the application using Pillow to open images. There is no indication of privilege escalation, data corruption, or remote code execution from this vulnerability.
Mitigation Recommendations
Upgrade to Pillow version 13.0.0 or later, where this vulnerability is fixed. No other mitigations are indicated or required.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-10-19T20:16:09.857Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ad697602cdf04f6569bbdc9
Added to database: 10/19/2026, 22:19:12 UTC
Last enriched: 10/19/2026, 22:33:24 UTC
Last updated: 10/19/2026, 22:48:20 UTC
Views: 6
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