In PHP versions 7.3.x below 7.3.27, 7.4.x below 7.4.15 and 8.0.x below 8.0.2, when using SOAP extension to connect to a SOAP server, a malicious SOAP server could return malformed XML data as a response that would cause PHP to access a null pointer and thus cause a crash.
https://www.tenable.com/security/tns-2021-14
https://www.oracle.com/security-alerts/cpuoct2021.html
https://www.debian.org/security/2021/dsa-4856
https://security.netapp.com/advisory/ntap-20210312-0005/
https://security.gentoo.org/glsa/202105-23
https://lists.debian.org/debian-lts-announce/2021/07/msg00008.html