CVE-2026-27026CWE-770

pypdf possibly has long runtimes for malformed FlateDecode streams

Medium · published February 20, 2026

CVSS v4.0
6.9
EPSS
0%
Percentile
10.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
6.9 · MEDIUM
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
EPSS
0.00206 · 10.1th percentile
Weakness
CWE-770 · Allocation of Resources Without Limits or Throttling
Published
2026-02-20T21:12Z
EPSS history
Timeline
  • 20 FEB 21:12Z
    pypdf possibly has long runtimes for malformed FlateDecode streams
    cvelistv5