Pillow JPEG2000 tiled decode retains a growing scratch buffer and can be used for denial of service

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-59204: 0.39% estimated exploitation activity in the next 30 days; percentile 32.66 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary src/libImaging/Jpeg2KDecode.c:853 accumulates totalcomponentwidth across every tile in a JPEG2000 image instead of recomputing it per tile. That accumulated value is then used in the tilebytes calculation at src/libImaging/Jpeg2KDecode.c:868, which can make the decoder grow state-buffer via realloc at src/libImaging/Jpeg2KDecode.c:876 up to roughly one full image's decompressed size even when each tile is small. A crafted tiled JPEG2000 file can therefore force substantially higher transient memory usage and trigger out-of-memory failures during decoding. Based on current evidence, the supported impact is denial of service, not memory corruption. Details - Location: src/libImaging/Jpeg2KDecode.c:853 - Root cause: totalcomponentwidth is initialized only once before the tile loop and keeps growing across tiles. It is then used to derive tilebytes, so later tiles are treated as if they had the combined component width of all earlier tiles. - Dangerous operation: tilebytes is…

Published by the source

20 Jul 2026, 23:18 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 13:49 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-vjc4-5qp5-m44j

2. Revision 2 · amended · 25 Oct 2026

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

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-vjc4-5qp5-m44j

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# Patch Next advisory brief: CVE-2026-59204

Advisory: Pillow JPEG2000 tiled decode retains a growing scratch buffer and can be used for denial of service
IDs: CVE-2026-59204, GHSA-vjc4-5qp5-m44j
Record: https://patchnext.com/advisories/cve-2026-59204 (revision 3, source checked 26 Oct 2026, 13:49 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: pillow 12.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI pillow: affected >= 8.2.0, < 12.3.0; fixed in 12.3.0

## 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-vjc4-5qp5-m44j (OSV record GHSA-vjc4-5qp5-m44j lists affected ranges: PyPI pillow >=8.2.0 <12.3.0 (fixed))
- Verified: https://github.com/advisories/GHSA-vjc4-5qp5-m44j (GitHub-reviewed advisory GHSA-vjc4-5qp5-m44j lists affected ranges: PyPI pillow >=8.2.0 <12.3.0)

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