greeter crashes on empty username

Bug #1266449 reported by Guido Berhoerster
This bug affects 1 person
Affects Status Importance Assigned to Milestone
LightDM GTK Greeter
Fix Released
lightdm-gtk-greeter (Debian)

Bug Description

lightdm-gtk-greeter uses the lightdm-gobject API incorrectly and does not handle the possibility of lightdm_greeter_get_authentication_user() returning NULL when the username of the previous authentication is invalid, i.e. when it was empty, resulting in a NULL pointer dereference in start_authentication().

Revision history for this message
Guido Berhoerster (gber) wrote :

This is a security issue due to the possibility of a local denial of service. A CVE has been requested at

information type: Public → Public Security
Revision history for this message
Yves-Alexis Perez (corsac) wrote :

I can confirm on Debian sid with 1.6. Here's a patch against our package, taken from the Suse report. There are other strcmp() which might need checking too.

Revision history for this message
Sean Davis (bluesabre) wrote :

Thanks everyone, fixed in trunk.

Changed in lightdm-gtk-greeter:
status: New → Fix Committed
milestone: none → 1.7.1
Sean Davis (bluesabre)
Changed in lightdm-gtk-greeter:
status: Fix Committed → Fix Released
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