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Vulnerability record · CVE-2019-12519 · published 15 April 2020

CVE-2019-12519: Squid-cache squid out-of-bounds write vulnerability

Squid Cache · Squid

An issue was discovered in Squid through 4.7. When handling the tag esi:when when ESI is enabled, Squid calls ESIExpression::Evaluate. This function uses a fixed stack buffer to hold the expression while it's being evaluated. When processing the expression, it could either evaluate the top of the stack, or add a new member to the stack. When adding a new member, there is no check to ensure that the stack won't overflow.

9.8 CVSS 3.1 Critical EPSS 6.7% · top 6.3% CWE-787 · Out-of-bounds write
9.8CVSS 3.1 base score, v2 7.5
6.7%EPSS exploitation probability, 30 days
NoNot in CISA KEV
4Affected product versions listed by NVD
16References
17 Jun 2026Last modified by NVD

Description

An issue was discovered in Squid through 4.7. When handling the tag esi:when when ESI is enabled, Squid calls ESIExpression::Evaluate. This function uses a fixed stack buffer to hold the expression while it's being evaluated. When processing the expression, it could either evaluate the top of the stack, or add a new member to the stack. When adding a new member, there is no check to ensure that the stack won't overflow.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

4 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00018.html Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2020/04/23/1 Mailing ListThird Party Advisory
https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12519.txt Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202005-05 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210205-0006/ Third Party Advisory
https://usn.ubuntu.com/4356-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4682 Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00018.html Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2020/04/23/1 Mailing ListThird Party Advisory
https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12519.txt Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202005-05 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210205-0006/ Third Party Advisory
https://usn.ubuntu.com/4356-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4682 Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2019-12519), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.