Check the REST API password in a way that is resistant to timing attacks. Using basic string equality is vulnerable to timing attacks as it will short circuit at the first wrong character. Using hmac.compare_digest avoids that issue and will take the same time, regardless of whether the value is correct or not. This is only exploitable if an attacker can talk directly to the REST API, which by default is bound to localhost. Reference: https://bugs.gentoo.org/828115
Created mailman tracking bugs for this issue: Affects: fedora-34 [bug 2047792]
Created mailman3 tracking bugs for this issue: Affects: fedora-all [bug 2048605]
Upstream patch: https://gitlab.com/mailman/mailman/-/commit/e4a39488c4510fcad8851217f10e7337a196bb51
Marking all RHEL mailman versions as not affected because the versions shipped there are based on mailman 2 which does not have the REST API which is used in this vulnerability and that affects only mailman 3.
REST API was introduced in Mailman 3.0 alpha, see https://gitlab.com/mailman/mailman/-/blob/master/src/mailman/docs/NEWS.rst#alpha-3-working-man .