High 8.7Published Sep 30, 2026

CVE-2026-102997pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)

Updated under an hour ago (2026-10-19 09:10 UTC)

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It affects py-pdf pypdf and 1 other product. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.34%, higher than 26% of scored CVEs.

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Every CVE for py-pdf pypdf

Exploited in the last 30 days

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: 8.7 HIGH (v4.0, CNA)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
Weakness (CWE): CWE-400, CWE-407
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.34% (percentile 26)
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Oct 2, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

py-pdf pypdf py_pdf:pypdf (from the name)	before 6.18.1	CNA record
pypdf_project pypdf pypdf_project:pypdf	before 6.18.1	NVD

References

https://github.com/py-pdf/pypdf/security/advisories/GHSA-jw7q-gvrg-4vj3x-refsource-confirm, vendor-advisory
https://github.com/py-pdf/pypdf/pull/4073x-refsource-misc, patch, issue-tracking
https://github.com/py-pdf/pypdf/commit/d9d38cf99b115deb562d3b68f36c33027bc04f79x-refsource-misc, patch
https://github.com/py-pdf/pypdf/releases/tag/6.18.1x-refsource-misc, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.