DescriptionA vulnerability was found in FreeIPA in how the initial implementation of MS-SFU by MIT Kerberos was missing a condition for granting the "forwardable" flag on S4U2Self tickets. Fixing this mistake required adding a special case for the check_allowed_to_delegate() function: If the target service argument is NULL, then it means the KDC is probing for general constrained delegation rules and not checking a specific S4U2Proxy request. In FreeIPA 4.11.0, the behavior of ipadb_match_acl() was modified to match the changes from upstream MIT Kerberos 1.20. However, a mistake resulting in this mechanism applies in cases where the target service argument is set AND where it is unset. This results in S4U2Proxy requests being accepted regardless of whether or not there is a matching service delegation rule.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
freeipa (PTS)buster4.7.2-3vulnerable
buster (security)4.7.2-3+deb10u1vulnerable

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

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs


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