Pillow CVE-2026-42311
HIGH
GHSA-pwv6-vv43-88gr
CVSS VectorNVD
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
5Blast Radius
ecosystem impact- 355 pypi packages depend on pillow (296 direct, 65 indirect)
Ecosystem-wide dependent count for version 10.3.0.
DescriptionNVD
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)
AnalysisAI
Integer overflow in Pillow 10.3.0 through 12.1.1 bypasses bounds checks during PSD tile extent validation, enabling memory corruption and arbitrary code execution when processing malicious PSD files. This vulnerability (CVE-2026-42311) exploits an incomplete fix for CVE-2026-25990, where the original patch added tile extent validation but used overflow-prone integer types. …
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RemediationAI
Within 24 hours: Identify all systems and applications using Pillow versions 10.3.0-12.1.1 (check pip freeze, requirements.txt, Docker manifests, and dependency trees). Within 7 days: Deploy Pillow 12.2.0 or later across development, staging, and production environments; verify via pip show pillow. …
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External POC / Exploit Code
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