Several vulnerabilities were discovered in Heimdal, an implementation of Kerberos 5 that aims to be compatible with MIT Kerberos.
Joseph Sutton discovered that the Heimdal KDC does not validate that
the server name in the TGS-REQ is present before dereferencing,
which may result in denial of service.
It was discovered that Heimdal is prone to a NULL dereference in
acceptors where an initial SPNEGO token that has no acceptable
mechanisms, which may result in denial of service for a server
application that uses SPNEGO.
Several buffer overflow flaws and non-constant time leaks were
discovered when using 1DES, 3DES or RC4 (arcfour).
An out-of-bounds memory access was discovered when Heimdal
normalizes Unicode, which may result in denial of service.
It was discovered that integer overflows in PAC parsing may result
in denial of service for Heimdal KDCs or possibly Heimdal servers.
It was discovered that the Heimdal's ASN.1 compiler generates code
that allows specially crafted DER encodings to invoke an invalid
free on the decoded structure upon decode error, which may result in
remote code execution in the Heimdal KDC.
For the stable distribution (bullseye), these problems have been fixed in version 7.7.0+dfsg-2+deb11u2.
We recommend that you upgrade your heimdal packages.