Pillow: Controlled heap out-of-bounds write in `ImageCmsTransform.apply()` via output mode mismatch

Description

Pillow is a Python imaging library. Prior to 12.3.0, Pillow's ImageCms.ImageCmsTransform.apply(im, imOut) API can trigger controlled native heap corruption when the caller supplies an output image whose mode does not match the transform's declared output mode. This issue is fixed in version 12.3.0.

Scores

EPSS (exploitation in 30 days)

0.39% · top 67% of all CVEs (7 Nov 2026)

CISA SSVC

Exploitation: poc · Automatable: yes · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Weakness

• CWE-787: Out-of-bounds Write (opens in a new tab)All about CWE-787 and its CVEs

Affected products

• python-pillow · Pillow

  • affected < 12.3.0

Affected packages

From reviewed advisories of the GitHub Advisory Database.

• PyPIpillowGHSA-9hw9-ch79-4vh6 (opens in a new tab)

References (4)

• https://github.com/python-pillow/Pillow/security/advisories/GHSA-9hw9-ch79-4vh6 (opens in a new tab)x_refsource_CONFIRMexploit
• https://github.com/python-pillow/Pillow/pull/9715 (opens in a new tab)x_refsource_MISC
• https://github.com/python-pillow/Pillow/commit/a9ffc42bedf4fc0a7ef8d6486e7f9e81e3397721 (opens in a new tab)x_refsource_MISC
• https://github.com/python-pillow/Pillow/releases/tag/12.3.0 (opens in a new tab)x_refsource_MISC

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisory GHSA-9hw9-ch79-4vh6 (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-59205](https://trackcve.app/badge/CVE-2026-59205.svg)](https://trackcve.app/cve/CVE-2026-59205)

Record last updated 14 Jul 2026, 17:31 UTC.