CVE ID:	CVE-2019-12521
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.
Test IDs:	None available
Cross References:	Common Vulnerability Exposure (CVE) ID: CVE-2019-12521 Debian Security Information: DSA-4682 (Google Search) https://www.debian.org/security/2020/dsa-4682 https://security.gentoo.org/glsa/202005-05 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 http://www.openwall.com/lists/oss-security/2020/04/23/1 SuSE Security Announcement: openSUSE-SU-2020:0623 (Google Search) http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00018.html https://usn.ubuntu.com/4356-1/