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8.7 High

pypdf is a free and open-source pure-python PDF library.

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.

Assessment

CVSS
8.7 (v4.0)
Severity
High
EPSS
0.34% chance of exploitation in the next 30 days
Known exploited
Not listed in CISA KEV
Exploit availability
Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published
30 September 2026
Last updated
2 November 2026
Affected
py-pdf · pypdf · pypdf
Weakness
CWE-400, CWE-407
Assigner
security-advisories@github.com

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

At the source

References

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