In libexpat in Expat before 2.2.7, XML input including XML names that contain a large number of colons could make the XML parser consume a high amount of RAM and CPU resources while processing (enough to be usable for denial-of-service attacks).
https://www.tenable.com/security/tns-2021-11
https://www.oracle.com/security-alerts/cpuoct2021.html
https://www.oracle.com/security-alerts/cpuoct2020.html
https://www.oracle.com/security-alerts/cpuapr2020.html
https://www.oracle.com/security-alerts/cpuApr2021.html
https://www.debian.org/security/2019/dsa-4472
https://usn.ubuntu.com/4040-2/
https://usn.ubuntu.com/4040-1/
https://support.f5.com/csp/article/K51011533
https://security.netapp.com/advisory/ntap-20190703-0001/
https://security.gentoo.org/glsa/201911-08
https://seclists.org/bugtraq/2019/Jun/39
https://lists.debian.org/debian-lts-announce/2019/06/msg00028.html
https://github.com/libexpat/libexpat/pull/262/commits/11f8838bf99ea0a6f0b76f9760c43704d00c4ff6
https://github.com/libexpat/libexpat/pull/262
https://github.com/libexpat/libexpat/issues/186
https://github.com/libexpat/libexpat/blob/R_2_2_7/expat/Changes
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=5226
http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00039.html