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Fencer Vulns
medium 6.2

CVE-2023-36810 json

Quadratic runtime with malformed PDF missing xref marker in pypdf

published 2023-06-30 3 y ago modified 2026-11-02 6 d ago also GHSA-jrm6-h9cq-8gqw , PYSEC-2026-1837 , EUVD-2023-1837

cvss
6.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

Summary

pypdf is a pure-python PDF library capable of splitting, merging, cropping, and transforming the pages of PDF files. An attacker who uses this vulnerability can craft a PDF which leads to unexpected long runtime. This quadratic runtime blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage. This issue has been addressed in PR 808 and versions from 1.27.9 include this fix. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Patch / fix

  • pypi pypdf2 1.27.9
  • pypdf2 Debian 12 1.27.9-1

debian advisories DEBIAN-CVE-2023-36810

  • pypdf2 Ubuntu 20.04 LTS 1.26.0-3ubuntu1.20.04.2
  • pypdf2 Ubuntu 22.04 LTS 1.26.0-4ubuntu0.22.04.2
  • pypdf2 Ubuntu Pro 16.04 LTS 1.25.1-1ubuntu0.1~esm2
  • pypdf2 Ubuntu Pro 18.04 LTS 1.26.0-2ubuntu0.1~esm2

ubuntu advisories UBUNTU-CVE-2023-36810

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 y ago

Exploit prediction

0.63% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/py-pdf/pypdf/security/advisories/GHSA-jrm6-h9cq-8gqw referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/py-pdf/pypdf/issues/582 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.2 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
OSV 3.1 6.2 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 6.2 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
pypi pypdf2
<1.27.9
1.27.9

Affected products

  • py-pdf pypdf

Classification

Weakness
  • CWE-407 Inefficient Algorithmic Complexity

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.