Infinite Loop when a comment isn't followed by a character in pypdf

published 2023-06-27 3 y ago modified 2026-11-02 7 d ago also GHSA-4vvm-4w3v-6mr8 , PYSEC-2026-1835 , PYSEC-2026-3008 , EUVD-2023-1690

cvss: 6.2; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 29%
public exploits: 0; none known

pypdf is an open source, pure-python PDF library. In affected versions an attacker may craft a PDF which leads to an infinite loop if `__parse_content_stream` is executed. That is, for example, the case if the user extracted text from such a PDF. This issue was introduced in pull request #969 and resolved in pull request #1828. Users are advised to upgrade. Users unable to upgrade may modify the line `while peek not in (b"\r", b"\n")` in `pypdf/generic/_data_structures.py` to `while peek not in (b"\r", b"\n", b"")`.

Patch / fix

fixed in 3 distros 1 links 5

pypi pypdf 3.9.0
pypi pypdf2 3.9.0
py-pdf pypdf 3.9.0

pypdf Debian 12 3.4.1-1+deb12u1
pypdf Debian 14, Debian 13 3.17.4-1
pypdf2 Debian 12 2.12.1-3+deb12u1

debian advisories DEBIAN-CVE-2023-36464

github.com/py-pdf/pypdf@b0e5c68 commit
github.com/py-pdf/pypdf/security/advisories/GHSA-4vvm-4w3v-6mr8 patch
github.com/py-pdf/pypdf#1828 pull request
github.com/py-pdf/pypdf#969 pull request
github.com/py-pdf/pypdf/releases/tag/3.9.0 release

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2023-36464 updated 2026-11-02 cvss 6.2

pypdf: Possible Infinite Loop when a comment isn't followed by a character

Red Hat Quay v3 quay/quay-rhel8 v3.9.1-6
fixed: vendor fix RHBA-2023:4974
Red Hat Quay v3 quay/clair-rhel8 v3.9.1-1, quay/quay-builder-rhel8 v3.9.1-1, quay/quay-operator-rhel8 v3.9.1-2, quay/quay-operator-bundle v3.9.1-7, quay/quay-bridge-operator-rhel8 v3.9.1-2, quay/quay-bridge-operator-bundle v3.9.1-2, +3 more
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 23 mo ago (2024-12-03)

Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 29% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/py-pdf/pypdf/security/advisories/GHSA-4vvm-4w3v-6mr8 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	5.5	CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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
OSV	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	pypdf	>=3.1.0, <3.9.0	3.9.0
pypi	pypdf2	>=2.2.0, <=3.0.1 >=2.2.0, <3.9.0	3.9.0

Affected products

py-pdf pypdf

Classification

Weakness

CWE-835 Loop with Unreachable Exit Condition

References

github.com /py-pdf/pypdf/pull/1828
web, patch
github.com /py-pdf/pypdf/pull/969
web, issue-tracking, patch
github.com /py-pdf/pypdf/security/advisories/GHSA-4vvm-4w3v-6mr8
web, exploit, patch
github.com /py-pdf/pypdf/commit/b0e5c689df689ab173df84dacd77b6fc3c161932
web, patch
nvd.nist.gov /vuln/detail/CVE-2023-36464
advisory
github.com /py-pdf/pypdf
package
github.com /py-pdf/pypdf/releases/tag/3.9.0
web
pypi.org /project/pypdf
package
github.com /advisories/GHSA-4vvm-4w3v-6mr8
advisory
pypi.org /project/pypdf2
package

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.

Summary