What’s Vulnerable › Vulnerabilities

CVE-2019-12521

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 5.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-04-15 · updated 2026-06-17
• Weakness: CWE-193

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.

Affected products

• Canonical Ubuntu Linux: 16.04, 18.04, 19.10, 20.04
• Debian Linux: 9.0, 10.0
• openSUSE Leap: 15.1
• Squid: from 3.0 through 3.5.28; from 4.0 through 4.7; from 5.0 through 5.0.1

References

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

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