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High, CVSS 8.6amended

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

CVE-2026-42311GHSA-pwv6-vv43-88gr

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (pillow 12.2.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • PyPI pillow

    Affected
    >= 10.3.0, < 12.2.0
    Fixed in
    12.2.0

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
8.6 · 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 · score source
EPSS
  • CVE-2026-42311: 0.15% estimated exploitation activity in the next 30 days; percentile 4.17 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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)

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-pwv6-vv43-88gr

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-pwv6-vv43-88gr

Agent brief

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# Patch Next advisory brief: CVE-2026-42311

Advisory: Pillow has an OOB Write with Invalid PSD Tile Extents (Integer Overflow)
IDs: CVE-2026-42311, GHSA-pwv6-vv43-88gr
Record: https://patchnext.com/advisories/cve-2026-42311 (revision 3, source checked 26 Oct 2026, 13:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: pillow 12.2.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI pillow: affected >= 10.3.0, < 12.2.0; fixed in 12.2.0

## Suggested inspection (read-only)
- `python -m pip show pillow`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on pillow.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-pwv6-vv43-88gr (OSV record GHSA-pwv6-vv43-88gr lists affected ranges: PyPI pillow >=10.3.0 <12.2.0 (fixed))
- Verified: https://github.com/advisories/GHSA-pwv6-vv43-88gr (GitHub-reviewed advisory GHSA-pwv6-vv43-88gr lists affected ranges: PyPI pillow >=10.3.0 <12.2.0)

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