CVE-2026-96641Pillow: Reachable undefined behavior in native integer operations, potentially leading to denial of service or logic integrity compromise

Description

Pillow is a Python imaging library. Prior to 13.0.0, PILfont text-width accumulation in src/_imaging.c checks positive glyph advances against INT_MAX but does not check negative advances against INT_MIN. Repeating a signed 16-bit advance of -32768 can therefore execute a signed C integer overflow in xsize += dx, producing a large positive width from a negative mathematical result. Applications that use getlength(), getsize(), or derived layout, quota, serialization, or allocation calculations can experience logic-integrity errors or resource consumption, while the high-level mask path commonly retains a decompression-bomb check. This issue is fixed in version 13.0.0.

Data: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Published as the sources state it, in English.

Affected products and versions

Ubuntu fixes

• USN-9064-1 Pillow vulnerabilities Ubuntu 26.10, 26.04, 24.04, 22.04, 20.04, 18.04, 16.04, 14.04 · 12.11.2026 · pillow

References and patches

• https://github.com/python-pillow/Pillow/security/advisories/GHSA-4rm8-3hmm-39fg Vendor Advisory
• https://github.com/python-pillow/Pillow/pull/10010 Issue Tracking
• https://github.com/python-pillow/Pillow/commit/80de4be9e38d3a6148dd4d8491eb80cd12b760a4 Patch
• https://github.com/python-pillow/Pillow/releases/tag/13.0.0 Release Notes