GHSA-jr96-gvgh-j3r4: Pip/pypdf vulnerability

Q: What must an attacker provide to trigger the issue?

The attacker must supply a crafted PDF containing repeated malformed cross-reference streams. Processing that PDF can cause long runtimes.

Q: Which pypdf release contains the fix?

The issue is fixed in pypdf 6.21.2.

Q: What can be done if upgrading is not immediately possible?

Consider applying the changes from PR #4240 as a workaround.

Published Oct 23, 2026

Updated

Impact

An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires cross-reference streams with repeated malformed cross-reference streams.

Patches

This has been fixed in pypdf==6.21.2.

Workarounds

If you cannot upgrade yet, consider applying the changes from PR #4240.

Notes

This is a follow-up to https://github.com/py-pdf/pypdf/security/advisories/GHSA-55h5-xmcq-c37v, which had the side-effect of still loading the whole stream again despite the cache being present.

Affected Software

1 affected componentFixes available

pip/pypdf<6.21.2

6.21.2

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade pip/pypdf to a version that resolves this vulnerability.
Fixed in 6.21.2
Upgrade
Upgrade pypdf to a version that resolves this vulnerability.
Fixed in 6.21.2
Compensating control
If upgrading is not yet possible, apply the changes from PR #4240 to pypdf.

Event History

Oct 23, 2026

Advisory Published

via GitHub·08:54 PM

Data Sourced

via GitHub·08:54 PM

DescriptionWeaknessAffected Software

Frequently Asked Questions

What must an attacker provide to trigger the issue?

The attacker must supply a crafted PDF containing repeated malformed cross-reference streams. Processing that PDF can cause long runtimes.

Which pypdf release contains the fix?

The issue is fixed in pypdf 6.21.2.

What can be done if upgrading is not immediately possible?

Consider applying the changes from PR #4240 as a workaround.

GHSA-jr96-gvgh-j3r4: Pip/pypdf vulnerability

Affected Software

Remediation

Event History

Frequently Asked Questions

What must an attacker provide to trigger the issue?

Which pypdf release contains the fix?

What can be done if upgrading is not immediately possible?

Company

Resources

Contact

Frequently Asked Questions

What must an attacker provide to trigger the issue?

Which pypdf release contains the fix?

What can be done if upgrading is not immediately possible?