CVE-2026-102997

pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.

CVSS 4.0

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

CVSS 3.1

7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

0.3% chance of exploitation in the next 30 days; higher than 27% of CVEs (scores of 2026-10-25)

CWEs

CWE-400, CWE-407

Published

2026-09-30

Modified

2026-10-05

Record from

the NVD, synced 2026-10-19

Affected

• pypdf_project:pypdf

Packages (OSV)

References

• https://github.com/py-pdf/pypdf/commit/d9d38cf99b115deb562d3b68f36c33027bc04f79
• https://github.com/py-pdf/pypdf/pull/4073
• https://github.com/py-pdf/pypdf/releases/tag/6.18.1
• https://github.com/py-pdf/pypdf/security/advisories/GHSA-jw7q-gvrg-4vj3

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