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TI-2023-18604 Aliases CVE-2023-36810GHSA-jrm6-h9cq-8gqw

Quadratic runtime with malformed PDF missing xref marker in pypdf

Priority LOW 30CWE-407Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-407.

Summary

pypdf is a pure-python PDF library capable of splitting, merging, cropping, and transforming the pages of PDF files. An attacker who uses this vulnerability can craft a PDF which leads to unexpected long runtime. This quadratic runtime blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage. This issue has been addressed in PR 808 and versions from 1.27.9 include this fix. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0063 50th percentileScored 2026-11-07
Public exploit Yes 2 exploit referencesTagged by NVD
Fix Fixed pypdf (py-pdf): 1.27.9PyPDF2 (PyPI): 1.27.9

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
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 1.27.91.27.9Patch availableCNA
—PyPDF2 (PyPI)before 1.27.91.27.9Patch availableGHSA-jrm6-h9cq-8gqw
  • pypdf Vendorpy-pdf Affected before 1.27.9 Fixed in 1.27.9 Patch available CNA
  • PyPDF2 (PyPI) Vendor— Affected before 1.27.9 Fixed in 1.27.9 Patch available GHSA-jrm6-h9cq-8gqw

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:py-pdf:pypdf:*:*:*:*:*:*:*:*up to 1.27.8Vulnerablepy-pdf
  • cpe:2.3:a:py-pdf:pypdf:*:*:*:*:*:*:*:* Versions up to 1.27.8 Vulnerable ·py-pdf

Remediation

  • Fix · CNA pypdf (py-pdf) Fixed in 1.27.9
  • Fix · GHSA-jrm6-h9cq-8gqw PyPDF2 (PyPI) Fixed in 1.27.9 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2023-36810
  2. 2026-10-03 Alias added: GHSA-jrm6-h9cq-8gqw
  3. 2026-10-27 EPSS moved to the 50th–90th percentile

References

Exploit 2

Patch 1

Advisory 1

Other 3

  • 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