setpwnam.c in the util-linux package, as included in Red Hat Linux 7.3 and earlier, and other operating systems, does not properly lock a temporary file when modifying /etc/passwd, which may allow local users to gain privileges via a complex race condition that uses an open file descriptor in utility programs such as chfn and chsh.
http://www.securityfocus.com/bid/5344
http://www.redhat.com/support/errata/RHSA-2002-137.html
http://www.linux-mandrake.com/en/security/2002/MDKSA-2002-047.php
http://www.kb.cert.org/vuls/id/405955
http://www.iss.net/security_center/static/9709.php
http://rhn.redhat.com/errata/RHSA-2002-132.html
http://online.securityfocus.com/advisories/4320
http://marc.info/?l=bugtraq&m=102795787713996&w=2
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000523
http://archives.neohapsis.com/archives/bugtraq/2002-07/0396.html
http://archives.neohapsis.com/archives/bugtraq/2002-07/0357.html