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TI-2026-18218 Aliases CVE-2026-22691GHSA-4f6g-68pf-7vhv

pypdf has possible long runtimes for malformed startxref

Priority LOW 20CWE-1333Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · Low
Fix status
Partial Red Hat: 4 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-1333.

Summary

pypdf is a free and open-source pure-python PDF library. Prior to version 6.6.0, pypdf has possible long runtimes for malformed startxref. An attacker who uses this vulnerability can craft a PDF which leads to possibly long runtimes for invalid startxref entries. When rebuilding the cross-reference table, PDF files with lots of whitespace characters become problematic. Only the non-strict reading mode is affected. Only the non-strict reading mode is affected. This issue has been patched in version 6.6.0.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00433 37th percentileScored 2026-11-07
Fix Partial pypdf (py-pdf): 6.6.0pypdf (PyPI): 6.6.0Red Hat: 4 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
py-pdfpypdfbefore 6.6.06.6.0Patch availableCNA
—pypdf (PyPI)before 6.6.06.6.0Patch availableGHSA-4f6g-68pf-7vhv
  • pypdf Vendorpy-pdf Affected before 6.6.0 Fixed in 6.6.0 Patch available CNA
  • pypdf (PyPI) Vendor— Affected before 6.6.0 Fixed in 6.6.0 Patch available GHSA-4f6g-68pf-7vhv

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:py-pdf:pypdf:*:*:*:*:*:*:*:*before 6.6.0Vulnerablepy-pdf
  • cpe:2.3:a:py-pdf:pypdf:*:*:*:*:*:*:*:* Versions before 6.6.0 Vulnerable ·py-pdf

Remediation

  • Fix · CNA pypdf (py-pdf) Fixed in 6.6.0
  • Fix · GHSA-4f6g-68pf-7vhv pypdf (PyPI) Fixed in 6.6.0 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
OpenShift LightspeedAffectedNo fix yet: Fix deferred
Red Hat Ansible Automation Platform 2AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux AI (RHEL AI) 3AffectedNo fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)AffectedNo fix yet: Fix deferred

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-22691
  2. 2026-10-03 Alias added: GHSA-4f6g-68pf-7vhv

References

Patch 2

Advisory 2

Other 2

  • TI-2023-18601 Infinite Loop when reading malformed objects in pypdf CVSS 3.1MEDIUM 6.5
  • TI-2023-18305 Infinite Loop when a comment isn't followed by a character in pypdf CVSS 3.1MEDIUM 6.2
  • TI-2026-42743 pypdf: Possible infinite loop for not terminated inline images CVSS 4.0HIGH 8.7
  • TI-2026-42742 pypdf: Possible infinite loop for not terminated inline images (ASCII85 and ASCIIHex filter) CVSS 4.0HIGH 8.7
  • TI-2026-65557 pypdf: Possible large memory usage when retrieving alphabetical page labels CVSS 4.0HIGH 8.7
  • TI-2026-65556 pypdf: Possible long runtimes with large amount of embedded files CVSS 4.0HIGH 8.7
See all 65 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences