How severe is CVE-2026-42311?

No CVSS score has been assigned to CVE-2026-42311 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-42311?

CVE-2026-42311 affects the following packages: pillow (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-42311?

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.

How do I detect CVE-2026-42311 in my PyPI dependencies?

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.

How do I mitigate CVE-2026-42311 if there is no patch (or I can't update yet)?

Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Is CVE-2026-42311 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42311 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-42311?

CVE-2026-42311 has an EPSS (Exploit Prediction Scoring System) score of 0.1%, placing it in the 4th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-42311?

CVE-2026-42311 is classified as CWE-190 (CWE-190), Out-of-bounds Write (CWE-787). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-42311 published, and has it been updated?

CVE-2026-42311 was published on May 9, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

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

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 4, 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 CVEs4th percentile — riskier than 4% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

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

Fix: https://github.com/python-pillow/Pillow/pull/9520
Original issue: CVE-2026-25990 (Pillow 12.1.1)

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`pillow`	≥ 10.3.0&&< 12.2.0	12.2.0`pip install --upgrade 'pillow==12.2.0'`

Affected Products

1 product · 1 configurations

Application

pillowpython

≥ 10.3.0 && < 12.2.0

range

Detection & mitigation playbook

Open-source dependency

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.
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.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

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…

Workaround published by Red Hat

To mitigate this vulnerability, users should avoid processing untrusted or suspicious PSD image files with applications that utilize the Pillow library. Implementing strict input validation and sanitization for image uploads and processing workflows can reduce the risk. Additionally, running applications that process untrusted content within a sandboxed environment can limit the potential impact of successful exploitation.

Source: Red Hat security advisory for CVE-2026-42311 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat AI Inference Server 3.2	`rhaiis/model-opt-cuda-rhel9:1787772157`	RHSA-2026:61628
Red Hat AI Inference Server 3.3	`rhaiis/model-opt-cuda-rhel9:1778244559`	RHSA-2026:16008
Red Hat AI Inference Server 3.3	`rhaiis/vllm-rocm-rhel9:1778244531`	RHSA-2026:16009
Red Hat AI Inference Server 3.3	`rhaiis/vllm-cuda-rhel9:1778274666`	RHSA-2026:16030
Red Hat AI Inference Server 3.4	`rhaii/vllm-spyre-rhel9:1787151840`	RHSA-2026:57387
Red Hat AI Inference Server 3.4	`rhaii/vllm-spyre-rhel9:1789681201`	RHSA-2026:69464
Red Hat AI Inference Server 3.4	`rhaii/vllm-spyre-rhel9:1790076141`	RHSA-2026:70969
Red Hat OpenShift AI 3.4	`rhoai/odh-automl-rhel9:1786612415`	RHSA-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

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