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Fencer Vulns
medium 6.2

CVE-2023-36807 json

Infinite Loop when reading malformed objects in pypdf

published 2023-06-30 3 y ago modified 2026-11-02 6 d ago also GHSA-hm9v-vj3r-r55m , PYSEC-2026-1836 , EUVD-2023-1823

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 47%
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. In version 2.10.5 an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This infinite loop blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage. That is, for example, the case if the user extracted metadata from such a malformed PDF. Versions prior to 2.10.5 throw an error, but do not hang forever. This issue was fixed with https://github.com/py-pdf/pypdf/pull/1331 which has been included in release 2.10.6. Users are advised to upgrade. Users unable to upgrade should modify `PyPDF2/generic/_data_structures.py::read_object` to an an error throwing case. See GHSA-hm9v-vj3r-r55m for details.

Patch / fix

  • pypi pypdf2 2.10.6
  • pypdf2 Debian 12 2.10.7-1

debian advisories DEBIAN-CVE-2023-36807

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
2 y ago

Exploit prediction

0.57% chance of exploitation in the next 30 days, higher than 47% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/py-pdf/pypdf/security/advisories/GHSA-hm9v-vj3r-r55m referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/py-pdf/pypdf/issues/1329 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
>=2.10.5, <2.10.6
2.10.6

Affected products

  • py-pdf pypdf
  • pypdf_project pypdf

Classification

Weakness
  • CWE-835 Loop with Unreachable Exit Condition

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.