What’s Vulnerable › Vulnerabilities

CVE-2023-36810: Quadratic runtime with malformed PDF missing xref marker in pypdf

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2023-06-30 · updated 2026-06-17
• Weakness: CWE-407

Description

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.

Affected products

• py-pdf pypdf: through 1.27.8

References

• https://github.com/py-pdf/pypdf/issues/582
• https://github.com/py-pdf/pypdf/pull/808
• https://github.com/py-pdf/pypdf/security/advisories/GHSA-jrm6-h9cq-8gqw
• https://lists.debian.org/debian-lts-announce/2023/07/msg00019.html
• https://github.com/py-pdf/pypdf/issues/582
• https://github.com/py-pdf/pypdf/pull/808
• https://github.com/py-pdf/pypdf/security/advisories/GHSA-jrm6-h9cq-8gqw
• https://lists.debian.org/debian-lts-announce/2023/07/msg00019.html

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