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.

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Fixes

Solution

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Workaround

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History

Thu, 01 Oct 2026 06:30:00 +0000

Type Values Removed Values Added
First Time appeared Py-pdf
Py-pdf pypdf
Vendors & Products Py-pdf
Py-pdf pypdf

Thu, 01 Oct 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-835
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Important


Wed, 30 Sep 2026 20:30:00 +0000

Type Values Removed Values Added
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.
Title pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
Weaknesses CWE-400
CWE-407
References
Metrics cvssV4_0

{'score': 8.7, 'vector': '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'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-30T20:05:51.538Z

Reserved: 2026-09-29T20:46:08.335Z

Link: CVE-2026-102997

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-30T21:17:07.020

Modified: 2026-10-01T02:17:43.350

Link: CVE-2026-102997

cve-icon Redhat

Severity : Important

Publid Date: 2026-09-30T20:05:51Z

Links: CVE-2026-102997 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-01T06:15:14Z

Weaknesses