PYSEC-2026-4156

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Import Source
https://github.com/pypa/advisory-database/blob/main/vulns/pypdf/PYSEC-2026-4156.yaml
JSON Data
https://api.osv.dev/v1/vulns/PYSEC-2026-4156
Aliases
Published
2026-10-01T16:44:33Z
Modified
2026-10-01T17:45:17Z
Severity
  • 8.7 (High) CVSS_V4 - 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 CVSS Calculator
Summary
pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
Details

Impact

An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a partially malformed /FlateDecode stream, where the byte-by-byte decompression is used.

Patches

This has been fixed in pypdf==6.18.1.

Workarounds

If you cannot upgrade yet, consider applying the changes from PR #4073.

References

Affected packages

PyPI / pypdf

Package

Name
pypdf
View open source insights on deps.dev
Purl
pkg:pypi/pypdf

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
6.18.1

Affected versions

1.*
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
1.11
1.12
1.13
3.*
3.1.0
3.2.0
3.2.1
3.3.0
3.4.0
3.4.1
3.5.0
3.5.1
3.5.2
3.6.0
3.7.0
3.7.1
3.8.0
3.8.1
3.9.0
3.9.1
3.10.0
3.11.0
3.11.1
3.12.0
3.12.1
3.12.2
3.13.0
3.14.0
3.15.0
3.15.1
3.15.2
3.15.3
3.15.4
3.15.5
3.16.0
3.16.1
3.16.2
3.16.3
3.16.4
3.17.0
3.17.1
3.17.2
3.17.3
3.17.4
4.*
4.0.0
4.0.1
4.0.2
4.1.0
4.2.0
4.3.0
4.3.1
5.*
5.0.0
5.0.1
5.1.0
5.2.0
5.3.0
5.3.1
5.4.0
5.5.0
5.6.0
5.6.1
5.7.0
5.8.0
5.9.0
6.*
6.0.0
6.1.0
6.1.1
6.1.2
6.1.3
6.2.0
6.3.0
6.4.0
6.4.1
6.4.2
6.5.0
6.6.0
6.6.1
6.6.2
6.7.0
6.7.1
6.7.2
6.7.3
6.7.4
6.7.5
6.8.0
6.9.0
6.9.1
6.9.2
6.10.0
6.10.1
6.10.2
6.11.0
6.12.0
6.12.1
6.12.2
6.13.0
6.13.1
6.13.2
6.13.3
6.14.0
6.14.1
6.14.2
6.15.0
6.16.0
6.16.1
6.16.2
6.17.0
6.18.0

Database specific

source 
"https://github.com/pypa/advisory-database/blob/main/vulns/pypdf/PYSEC-2026-4156.yaml"