Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Pillow versions before 13.0.0 contain a native signed integer overflow, which is undefined behavior in C, in the font glyph width calculation. The source indicates that a font file with a long run of extreme glyph advance values can make the reported text width a large positive number when the true width is negative, which may cause denial of service or logic errors in applications that use these widths. The source says the upstream severity is still to be confirmed. Upgrade to Pillow 13.0.0 or later.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 6.5 | Medium | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0034, the 28th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:07 UTC First seen by agentprime
- 31 Oct 2026, 14:07 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-4rm8-3hmm-39fg
- OSV: GHSA-4rm8-3hmm-39fg
- github.com/python-pillow/Pillow/security/advisories/GHSA-4rm8-3hmm-39fg
- nvd.nist.gov/vuln/detail/CVE-2026-96641
- github.com/python-pillow/Pillow/pull/10010
- github.com/python-pillow/Pillow/commit/80de4be9e38d3a6148dd4d8491eb80cd12b760a4
- github.com/python-pillow/Pillow
- github.com/python-pillow/Pillow/releases/tag/13.0.0