[ANNOUNCEMENT] CVE-2016-3067: network privilege escalation in Cygwin set(e)uid

[Yaakov Selkowitz]

In versions of Cygwin prior to 2.5.0, a process which switched user 
contexts on a system where neither the Cygwin LSA module was enabled, 
nor the user password stored thereon with 'passwd -R', would retain the 
network credentials of the original user context even after switching. 
In the case of system services, such as a user which logged into a 
Cygwin SSHD or a command run from a cronjob, this would allow access to 
networks shares to which the system service account (normally 
'cyg_server', which is in the Administrators group) has access but to 
which the user would otherwise be denied.

This issue was reported[1][2] by David Willis on 2016-Feb-08 and a fix 
committed[3] to the upstream repository by Corinna Vinschen on 
2016-Feb-18.  The fix was first included in the 2.5.0-0.4 test release 
on the same day[4] and in the 2.5.0-1 stable release which shipped[5] on 
2016-Apr-11.

Red Hat Product Security has assigned CVE-2016-3067 for this issue.

[1] https://cygwin.com/ml/cygwin/2016-02/msg00101.html
[2] https://cygwin.com/ml/cygwin/2016-02/msg00129.html and thread
[3] 
https://sourceware.org/git/?p=newlib-cygwin.git;a=commit;h=205862ed08649df8f50b926a2c58c963f571b044
[4] https://cygwin.com/ml/cygwin-announce/2016-02/msg00023.html
[5] https://cygwin.com/ml/cygwin-announce/2016-04/msg00020.html

-- 
Yaakov

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