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CVE-2026-42311 — pillow

Fix: python-pillow/Pillow@58f9a1d

CVE-2026-42311 is a CWE-190 vulnerability in pillow. A fix is available for pillow — see the affected versions and patch details below.

Pillow: OOB Write with Invalid PSD Tile Extents (Integer Overflow)

Also known asBIT-pillow-2026-42311GHSA-pwv6-vv43-88grPYSEC-2026-2252
Published
May 9, 2026
Updated
Aug 12, 2026
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Sep 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42311.

EPSS Exploitation Probability

via FIRST.org ↗
0.1%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs5th percentile — riskier than 5% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

1 pkg affected
🐍pillow

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

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

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIpillow≥ 10.3.0&&< 12.2.012.2.0pip install --upgrade 'pillow==12.2.0'

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pillow, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update pillow to 12.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42311 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-42311 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-42311. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

This is an Important severity flaw in Pillow, a Python imaging library, that could lead to arbitrary code execution. The vulnerability requires a user to process a specially crafted malicious PSD file, which could result in memory corruption and allow an attacker to execute arbitrary code. Red Hat products that…

ProductFixed inAdvisory
Red Hat AI Inference Server 3.2rhaiis/model-opt-cuda-rhel9:1787772157RHSA-2026:61628
Red Hat AI Inference Server 3.3rhaiis/model-opt-cuda-rhel9:1778244559RHSA-2026:16008
Red Hat AI Inference Server 3.3rhaiis/vllm-rocm-rhel9:1778244531RHSA-2026:16009
Red Hat AI Inference Server 3.3rhaiis/vllm-cuda-rhel9:1778274666RHSA-2026:16030
Red Hat AI Inference Server 3.4rhaii/vllm-spyre-rhel9:1787151840RHSA-2026:57387
Red Hat AI Inference Server 3.4rhaii/vllm-spyre-rhel9:1789681201RHSA-2026:69464
Red Hat OpenShift AI 3.4rhoai/odh-automl-rhel9:1786612415RHSA-2026:60520

Frequently Asked Questions

### 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/enco
O3 Security · Impact-Aware SCA

Is CVE-2026-42311 in your dependencies?

O3 Security finds CVE-2026-42311 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

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CVE-2026-42311: pillow RCE | O3 Security