CVE-2026-102997

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

State: Published
Severity: 8.7 High
Published: Sep 30, 2026
Updated: Oct 2, 2026
Reserved: Sep 29, 2026

Description

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.

Scores

CVSS	Score	Vector	Source
4.0	8.7 High	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	GitHub_M

Weaknesses

CWE-400 Uncontrolled Resource Consumption
CWE-407 Inefficient Algorithmic Complexity

Affected Products

Product	Versions
pypdfpy-pdf	< 6.18.1Affected

References

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