A flaw was discovered in gdm 3.24.1 where gdm greeter was no longer setting the ran_once boolean during autologin. If autologin was enabled for a victim, an attacker could simply select login as another user to unlock their screen.
Weakness
The product does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used.
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| Gnome_display_manager |
Gnome |
3.24.1 (including) |
3.24.1 (including) |
| Gdm3 |
Ubuntu |
artful |
* |
| Gdm3 |
Ubuntu |
devel |
* |
| Gdm3 |
Ubuntu |
zesty |
* |
Potential Mitigations
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
- For example, in Java, if the programmer does not explicitly initialize a variable, then the code could produce a compile-time error (if the variable is local) or automatically initialize the variable to the default value for the variable’s type. In Perl, if explicit initialization is not performed, then a default value of undef is assigned, which is interpreted as 0, false, or an equivalent value depending on the context in which the variable is accessed.
References