Date: Wed, 12 Jul 2017 10:43:50 +0200 From: Matthias Gerstner <mgerstner@...e.de> To: oss-security@...ts.openwall.com Subject: CVE-2017-11171: gnome-session: Bad reference counting in the context of accept_ice_connection() in gsm-xsmp-server.c Affected package: gnome-session Affected versions: < 2.29.92 Bad reference counting in the context of accept_ice_connection() in gsm-xsmp-server.c in old versions of gnome-session up until version 2.29.92 allows a local attacker to establish ICE connections to gnome-session with invalid authentication data (an invalid magic cookie). Each failed authentication attempt will leak a file descriptor in gnome-session. When the maximum number of file descriptors is exhausted in the gnome-session process, it will enter an infinite loop trying to communicate without success, consuming 100% of the CPU. The graphical session associated with the gnome-session process will stop working correctly, because communication with gnome-session is no longer possible. This was fixed with the following commit: https://github.com/GNOME/gnome-session/commit/b0dc999e0b45355314616321dbb6cb71e729fc9d The problem seems to be that upon connection establishment gms_store_add() is called, but not gsm_store_remove(), even if the authentication of the ICE connection fails. You can find a proof of concept program attached. References: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-11171 https://bugzilla.suse.com/show_bug.cgi?id=1048274 Regards Matthias -- Matthias Gerstner <matthias.gerstner@...e.de> Dipl.-Wirtsch.-Inf. (FH), Security Engineer https://www.suse.com/security Telefon: +49 911 740 53 290 SUSE Linux GmbH GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nuernberg) View attachment "ice_dos.c" of type "text/x-c" (3493 bytes) Download attachment "signature.asc" of type "application/pgp-signature" (820 bytes)
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