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From: ghudson@mit.edu
Subject: git commit
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Fix KDC null deref on TGS inner body null server

After the KDC decodes a FAST inner body, it does not check for a null
server.  Prior to commit 39548a5b17bbda9eeb63625a201cfd19b9de1c5b this
would typically result in an error from krb5_unparse_name(), but with
the addition of get_local_tgt() it results in a null dereference.  Add
a null check.

Reported by Joseph Sutton of Catalyst.

CVE-2021-37750:

In MIT krb5 releases 1.14 and later, an authenticated attacker can
cause a null dereference in the KDC by sending a FAST TGS request with
no server field.

https://github.com/krb5/krb5/commit/d775c95af7606a51bf79547a94fa52ddd1cb7f49
Author: Greg Hudson <ghudson@mit.edu>
Commit: d775c95af7606a51bf79547a94fa52ddd1cb7f49
Branch: master
 src/kdc/do_tgs_req.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)