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Vulnerability · Published Feb 20, 2026 · Assigned by GitHub_M

CVE-2026-27026pypdf possibly has long runtimes for malformed FlateDecode streams

Medium 6.9

In plain English

A medium-severity resource allocation without limits in pypdf from py-pdf. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 9% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.9Medium
Exploit odds (30 days)0.2%top 91.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a malformed /FlateDecode stream, where the byte-by-byte decompression is used. This vulnerability is fixed in 6.7.1.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12pypdfno fix listedDEBIAN-CVE-2026-27026
Debian:13pypdfno fix listedDEBIAN-CVE-2026-27026
Debian:14pypdf6.9.0-1DEBIAN-CVE-2026-27026
Debian:12pypdf2no fix listedDEBIAN-CVE-2026-27026
PyPIpypdf6.7.1GHSA-9mvc-8737-8j8h
PyPIpypdf6.7.1PYSEC-2026-3015
Ubuntu:24.04:LTSpypdfno fix listedUBUNTU-CVE-2026-27026
Ubuntu:25.10pypdfno fix listedUBUNTU-CVE-2026-27026
Ubuntu:26.04:LTSpypdfno fix listedUBUNTU-CVE-2026-27026
Ubuntu:26.10pypdfno fix listedUBUNTU-CVE-2026-27026
Ubuntu:22.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-27026
Ubuntu:24.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-27026

Affected products (as reported)

VendorProductVersions
py-pdf pypdf < 6.7.1

Weakness: CWE-770 · Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

References