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CVE-2026-54651

pypdf: Possible infinite loop when processing threads/articles in writer

6.9 MediumFix available

pypdf is a free and open-source pure-python PDF library. Prior to 6.13.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer. This vulnerability is fixed in 6.13.1.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.16%Unchanged since Jun 23, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.9

pypdf: Possible infinite loop when processing threads/articles in writer

pypdf is a free and open-source pure-python PDF library. Prior to 6.13.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer. This vulnerability is fixed in 6.13.1.

Record
CVE-2026-54651
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-835
Updated
2026-11-02
EUVDEUVD-2026-38358 6.9

pypdf is a free and open-source pure-python PDF library. Prior to 6.13.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer. This vulnerability is fixed in 6.13.1.

Record
EUVD-2026-38358
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-g9xf-7f8q-9mcj 6.9

pypdf: Possible infinite loop when processing threads/articles in writer

Impact

An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer.

Patches

This has been fixed in pypdf==6.13.1.

Workarounds

If users cannot upgrade yet, consider applying the changes from PR #3839.

Record
GHSA-g9xf-7f8q-9mcj
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-835
Updated
2026-11-02
NVD 6.9

pypdf is a free and open-source pure-python PDF library. Prior to 6.13.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer. This vulnerability is fixed in 6.13.1.

Record
CVE-2026-54651
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-835
Updated
2026-11-02
OSV 6.9

pypdf: Possible infinite loop when processing threads/articles in writer

pypdf is a free and open-source pure-python PDF library. Prior to 6.13.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer. This vulnerability is fixed in 6.13.1.

Record
CVE-2026-54651
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-835
Updated
2026-11-04
OSVDEBIAN-CVE-2026-54651 5.5

pypdf is a free and open-source pure-python PDF library. Prior to 6.13.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer. This vulnerability is fixed in 6.13.1.

Record
DEBIAN-CVE-2026-54651
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-03
Show 7 moreShow less
OSVGHSA-g9xf-7f8q-9mcj 6.9

pypdf: Possible infinite loop when processing threads/articles in writer

Impact

An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer.

Patches

This has been fixed in pypdf==6.13.1.

Workarounds

If users cannot upgrade yet, consider applying the changes from PR #3839.

Record
GHSA-g9xf-7f8q-9mcj
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-835
Updated
2026-11-02
OSVPYSEC-2026-3018 6.9

pypdf: Possible infinite loop when processing threads/articles in writer

Impact

An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer.

Patches

This has been fixed in pypdf==6.13.1.

Workarounds

If users cannot upgrade yet, consider applying the changes from PR #3839.

Record
PYSEC-2026-3018
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
OSVUBUNTU-CVE-2026-54651 6.9

pypdf is a free and open-source pure-python PDF library. Prior to 6.13.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer. This vulnerability is fixed in 6.13.1.

Record
UBUNTU-CVE-2026-54651
CVSS 4.0
6.9 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVCLSA-2026-1784077473 No score

TuxCare security update for pypdf (1 CVE)

TuxCare rebuilt pypdf to address 1 CVE. Fixed in 5.9.0.post11+tuxcare.

Record
CLSA-2026-1784077473
Updated
2026-11-02
OSVMGASA-2026-0577 No score

Updated python-pypdf package fixes security vulnerabilities

This new version fixes several security vulnerabilities.

Record
MGASA-2026-0577
Updated
2026-11-05
OSVopenSUSE-SU-2026:11113-1 No score

python311-pypdf-6.14.0-1.1 on GA media

These are all security issues fixed in the python311-pypdf-6.14.0-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:11113-1
Updated
2026-11-02
OSVROOT-APP-PYPI-CVE-2026-54651 No score

CVE-2026-54651 in pypdf - Patched by Root

Root has patched CVE-2026-54651 in the pypdf package for Root:PyPI. Multiple fixed versions available.

Record
ROOT-APP-PYPI-CVE-2026-54651
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
pypdf
PyPI
 before 6.13.1
6.13.1
pypdf
TuxCare:PyPI
 5.9.0 up to 5.9.0.post11+tuxcare, plus listed versions
5.9.0.post1+tuxcare5.9.0.post10+tuxcare5.9.0.post2+tuxcare5.9.0.post3+tuxcare5.9.0.post4+tuxcare
Show 5 moreShow less
5.9.0.post5+tuxcare5.9.0.post6+tuxcare5.9.0.post7+tuxcare5.9.0.post8+tuxcare5.9.0.post9+tuxcare
5.9.0.post11+tuxcare
pypdf
Debian:12
 All versions, plus listed versions
3.17.4-13.4.1-13.4.1-1+deb12u14.0.0-14.0.0-1~exp1
Show 13 moreShow less
4.0.1-14.0.2-14.1.0-14.2.0-14.3.1-15.4.0-16.19.0-16.21.0-16.21.1-16.21.4-16.9.0-16.9.2-16.9.2-2
 None known
pypdf
Debian:13
 All versions, plus listed versions
5.4.0-16.19.0-16.21.0-16.21.1-16.21.4-16.9.0-16.9.2-16.9.2-2
 None known
pypdf
Debian:14
 before 6.19.0-1, plus listed versions
5.4.0-16.9.0-16.9.2-16.9.2-2
6.19.0-1
pypdf2
Debian:12
 All versions, plus listed versions
2.12.1-32.12.1-3+deb12u12.12.1-4
 None known
pypdf
PyPI
 before 6.13.1, plus listed versions
1.01.11.101.111.12
Show 45 moreShow less
1.131.21.31.41.51.61.71.81.93.1.03.10.03.11.03.11.13.12.03.12.13.12.23.13.03.14.03.15.03.15.13.15.23.15.33.15.43.15.53.16.03.16.13.16.23.16.33.16.43.17.03.17.13.17.23.17.33.17.43.2.03.2.13.3.03.4.03.4.13.5.03.5.13.5.23.6.03.7.03.7.1
6.13.1
python-pypdf
Mageia:10
From an advisory covering 4 CVEs
 before 6.16.2-1.mga10
6.16.2-1.mga10
pypdf
Root:PyPI
 before 6.6.0+aikido.15
6.6.0+aikido.156.10.1+aikido.106.11.0+aikido.56.12.0+aikido.66.10.2+aikido.56.12.1+aikido.56.12.2+aikido.5
pypdf2
Ubuntu:Pro:16.04:LTS
 All versions, plus listed versions
1.23+git20141008-11.25.1-11.25.1-1ubuntu0.1~esm11.25.1-1ubuntu0.1~esm2
 None known
Show 10 moreShow less
Affected packages
PackageAffectedFixed
python-pypdf
Ubuntu:16.04:LTS
 All versions, plus listed versions
1:1.13-3
 None known
pypdf2
Ubuntu:Pro:18.04:LTS
 All versions, plus listed versions
1.26.0-21.26.0-2ubuntu0.1~esm11.26.0-2ubuntu0.1~esm2
 None known
pypdf2
Ubuntu:20.04:LTS
 All versions, plus listed versions
1.26.0-21.26.0-3ubuntu11.26.0-3ubuntu1.20.04.11.26.0-3ubuntu1.20.04.2
 None known
pypdf2
Ubuntu:22.04:LTS
 All versions, plus listed versions
1.26.0-41.26.0-4ubuntu0.22.04.11.26.0-4ubuntu0.22.04.2
 None known
pypdf
Ubuntu:24.04:LTS
 All versions, plus listed versions
3.4.1-13.17.4-14.0.0-14.0.1-14.0.2-1
 None known
pypdf2
Ubuntu:24.04:LTS
 All versions, plus listed versions
2.12.1-32.12.1-4
 None known
pypdf
Ubuntu:25.10
 All versions, plus listed versions
4.3.1-15.4.0-1
 None known
pypdf
Ubuntu:26.10
 All versions, plus listed versions
6.9.2-16.9.2-2
 None known
pypdf
Ubuntu:26.04:LTS
 All versions, plus listed versions
5.4.0-16.9.2-1
 None known
python-pypdf
openSUSE:Tumbleweed
 before 6.14.0-1.1
6.14.0-1.1

History

History
RecordedChangedSources
affected
affected, aliases, referencesOSV
factsOSV
affectedOSV
productsNVD
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-54651 is a medium vulnerability (CVSS 6.9) in Py-pdf Pypdf, published June 22, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.16%, the 5th percentile. Fixed in pypdf 6.13.1.

References

Show 8 moreShow less
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Left out here: 56 versions. The JSON record has them.

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