CVE-2019-12521

Name	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.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
References	DLA-2278-1, DSA-4682-1, ELA-271-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
squid (PTS)	buster (security), buster, buster (lts)	4.6-1+deb10u10	fixed
	bullseye (security), bullseye	4.13-10+deb11u3	fixed
	bookworm (security), bookworm	5.7-2+deb12u2	fixed
	sid, trixie	6.12-1	fixed
squid3 (PTS)	jessie, jessie (lts)	3.5.23-5+deb8u7	fixed
	stretch (security)	3.5.23-5+deb9u7	fixed
	stretch (lts), stretch	3.5.23-5+deb9u10	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Origin
squid	source	buster	4.6-1+deb10u2	DSA-4682-1
squid	source	(unstable)	4.11-1
squid3	source	jessie	3.5.23-5+deb8u1	ELA-271-1
squid3	source	stretch	3.5.23-5+deb9u2	DLA-2278-1
squid3	source	(unstable)	(unfixed)

Notes

http://www.squid-cache.org/Advisories/SQUID-2019_12.txt
Squid 4: http://www.squid-cache.org/Versions/v4/changesets/squid-4-fdd4123629320aa1ee4c3481bb392437c90d188d.patch