Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
pypdf versions before 6.18.1 are vulnerable to long runtimes when processing a PDF with a partially malformed FlateDecode stream that uses byte-by-byte decompression. An attacker who can supply a crafted PDF to an application that parses it can cause that processing to take a long time. Upgrade to pypdf 6.18.1 or later. The source gives few details on a workaround beyond a referenced code change, so upgrading is the recommended fix.
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 |
|---|---|---|---|---|
| 8.7 | High | 4.0 | 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 | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0034, the 27th percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 30 Sept 2026, 21:17 UTC Confirmed by NVD
- 31 Oct 2026, 14:09 UTC First seen by agentprime
- 31 Oct 2026, 14:09 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-jw7q-gvrg-4vj3
- OSV: GHSA-jw7q-gvrg-4vj3
- github.com/py-pdf/pypdf/security/advisories/GHSA-jw7q-gvrg-4vj3
- nvd.nist.gov/vuln/detail/CVE-2026-102997
- github.com/py-pdf/pypdf/pull/4073
- github.com/py-pdf/pypdf/commit/d9d38cf99b115deb562d3b68f36c33027bc04f79
- github.com/py-pdf/pypdf
- github.com/py-pdf/pypdf/releases/tag/6.18.1