Common Vulnerabilities and Exposures assigned an identifier CVE-2008-5006 to the following vulnerability: smtp.c in the c-client library in University of Washington IMAP Toolkit 2007b allows remote SMTP servers to cause a denial of service (NULL pointer dereference and application crash) by responding to the QUIT command with a close of the TCP connection instead of the expected 221 response code. References: http://www.openwall.com/lists/oss-security/2008/11/03/5
This source is also contained in pine (which we ship in RHEL2.1). It's unlikely that pine would ever be connecting to a malicious SMTP server.
The affected code is not used by any application shipped in Red Hat Enterprise Linux 2.1, 3, 4, and 5. The impact of this flaw is limited to a crash of the applications connecting to a misbehaving SMTP server. Due to those reasons, there's currently no plan to include the fix in the imap packages as shipped in Red Hat Enterprise Linux 2.1 and 3, and the libc-client packages as shipped in Red Hat Enterprise Linux 4 and 5. Version of uw-imap client packages as shipped in Fedora are already updated to upstream version 2007e, containing a fix for this issue.