Red Hat Bugzilla – Bug 208458
CVE-2006-5051 unsafe GSSAPI signal handler
Last modified: 2007-11-30 17:11:44 EST
+++ This bug was initially created as a clone of Bug #208347 +++
OpenSSH 4.4 was released and mentions:
* Fix an unsafe signal hander reported by Mark Dowd. The
signal handler was vulnerable to a race condition that could
be exploited to perform a pre-authentication denial of
service. On portable OpenSSH, this vulnerability could
theoretically lead to pre-authentication remote code execution
if GSSAPI authentication is enabled, but the likelihood of
successful exploitation appears remote.
-- Additional comment from email@example.com on 2006-09-28 11:17 EST --
I've done some analysis of this issue and received a mail from Mark Dowd
regarding this vulnerability. The upstream details are misleading.
The problem is that the signal handling in openssh does quite a lot and can
introduce a race condition during cleanup. This flaw could possibly cause a
double free condition within the kerberos cleanup code. The GSSAPI code is
completely harmless, upstream calling this issue a GSSAPI issue leads me to
believe they did not analyze, not try to understand this issue.
There is also PAM cleanup code which is executed. This PAM source hasn't been
investigated so the possible outcome is currently unknown.
Red Hat will be fixing this issue due to the incredible complexity and possible
danger. This is a case of better safe than sorry.
openssh-4.3p2-4.10 has been pushed for fc5, which should resolve this issue. If these problems are still present in this version, then please make note of it in this bug report.