Pillow has an OOB Write with Invalid PSD Tile Extents (Integer Overflow) (CVE-2026-42311)

Pillow has an OOB Write with Invalid PSD Tile Extents (Integer Overflow) (CVE-2026-42311) | HOL Guard CVE

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps pillow (pypi). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
pillowpypi	>=10.3.0 <12.2.0	12.2.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for pillow.
Review the reported fix. Update pillow to 12.2.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
May 4, 2026
Evidence: source:osv:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:record
First seen by HOL
Sep 10, 2026

Sources and claim methodology

Upstream source description

### Impact Processing a malicious PSD file could lead to memory corruption, potentially resulting in a crash or arbitrary code execution. ### Patches Patched version: 12.2.0 Pillow 12.1.1 addressed CVE-2026-25990 by adding checks for tile extents in PSD image decoding/encoding to prevent an out-of-bounds write. However, the bounds checks computed tile extent sums using types susceptible to integer overflow, meaning a PSD image with carefully chosen tile dimensions could produce values that wrap around and bypass the checks, still triggering an out-of-bounds write in src/decode.c and src/encode.c. The fix avoids adding extents together before comparison. ### Workarounds Use any version but affected versions: >= 10.3.0, < 12.2.0 ### Resources - Fix: https://github.com/python-pillow/Pillow/pull/9520 - Original issue: CVE-2026-25990 (Pillow 12.1.1)

Quoted source text, attributed separately from HOL analysis.