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Fix null deref in SPNEGO acceptor [CVE-2014-4344]

When processing a continuation token, acc_ctx_cont was dereferencing
the initial byte of the token without checking the length. This could
result in a null dereference.


In MIT krb5 1.5 and newer, an unauthenticated or partially
authenticated remote attacker can cause a NULL dereference and
application crash during a SPNEGO negotiation by sending an empty
token as the second or later context token from initiator to acceptor.
The attacker must provide at least one valid context token in the
security context negotiation before sending the empty token. This can
be done by an unauthenticated attacker by forcing SPNEGO to
renegotiate the underlying mechanism, or by using IAKERB to wrap an
unauthenticated AS-REQ as the first token.


[ CVE summary, CVSSv2 vector]

(cherry picked from commit 524688ce87a15fc75f87efc8c039ba4c7d5c197b)
Author: Greg Hudson <>
Committer: Tom Yu <>
Commit: 90df9bcfe3124ccac2cf2399e3286103076a2271
Branch: krb5-1.11
src/lib/gssapi/spnego/spnego_mech.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)