REDHAT-BUG-2533698: Low severity gssapi/gss-ntlmssp vulnerability

gss-ntlmssp (gssapi/gss-ntlmssp) contains a memory leak in the NTLM CHALLENGE target-info parsing on the client (initiator) path. The function ntlmdecodeavpairu16lstr() in src/ntlm.c (line 444) allocates a buffer via malloc and assigns it to str (line 464) without freeing any previous value. The caller ntlmdecodetargetinfo() (line 637) iterates over AVPAIRs in a while loop and decodes each string-valued AVPAIR (MSVAVNBCOMPUTERNAME, MSVAVNBDOMAINNAME, MSVAVDNSCOMPUTERNAME, MSVAVDNSDOMAINNAME, MSVAVDNSTREENAME, MSVAVTARGETNAME) into local variables. If a CHALLENGE message contains a duplicated string-valued AVPAIR ID, the second call overwrites the local pointer without freeing the first allocation. The done: cleanup only frees the last value held. The acceptor path (gsssecctx.c:843) passes NULL for all six string out-parameters, so the leak does not fire server-side. The initiator path is reachable via ntlmprocesstargetinfo() (src/ntlm.c:765), called from gssntlmcliauth() in src/gssauth.c:85, which passes all six string parameters non-NULL. The unguarded allocation predates the February 2023 security batch (GHSL-2023-011/012/013) and was not caught because oss-fuzz drives the acceptor entry point which never runs the string decode. By inspection, all released versions are affected. Reported by Chase Bevan-Thomas (cbev0x), independent security researcher. No upstream fix available at time of report. PSIRT Ticket: PSIRTSUPT-23614. Verified via static analysis in Kaiden sandbox.