In hpack_dht_insert in hpack-tbl.c in the HPACK decoder in HAProxy 1.8 through 2.x before 2.1.4, a remote attacker can write arbitrary bytes around a certain location on the heap via a crafted HTTP/2 request, possibly causing remote code execution.
https://www.mail-archive.com/haproxy%40formilux.org/msg36876.html
https://www.haproxy.org/download/2.1/src/CHANGELOG
https://www.debian.org/security/2020/dsa-4649
https://usn.ubuntu.com/4321-1/
https://security.gentoo.org/glsa/202012-22
https://lists.debian.org/debian-security-announce/2020/msg00052.html
https://git.haproxy.org/?p=haproxy.git%3Ba=commit%3Bh=5dfc5d5cd0d2128d77253ead3acf03a421ab5b88
https://bugzilla.suse.com/show_bug.cgi?id=1168023
https://bugzilla.redhat.com/show_bug.cgi?id=1819111
http://packetstormsecurity.com/files/157323/haproxy-hpack-tbl.c-Out-Of-Bounds-Write.html
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00002.html