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vulnerability announce CVE-2011-4073

Openswan: denial of service via Crypto Helper

Synthesis of the vulnerability

When Openswan uses a Crypto Helper, a remote attacker can interrupt an IKE session, in order to stop the pluto daemon.
Vulnerable products: Debian, Fedora, Openswan, RHEL, SUSE Linux Enterprise Desktop, SLES.
Severity of this weakness: 2/4.
Consequences of an attack: denial of service on service.
Hacker's origin: internet client.
Creation date: 02/11/2011.
Références of this bulletin: BID-50440, CVE-2011-4073, DSA-2374-1, FEDORA-2011-15077, FEDORA-2011-15127, FEDORA-2011-15196, MDVSA-2013:231, RHSA-2011:1422-01, SUSE-SU-2011:1310-1, SUSE-SU-2011:1311-1, VIGILANCE-VUL-11112.

Description of the vulnerability

The pluto IKE daemon of Openswan can be configured with Crypto Helpers, which do cryptographic tasks in distinct processes, so the daemon is not slowed down.

A client can connect to the daemon and do an ISAKMP Phase 1 authentication. The phase 2 is then done by a Crypto Helper. However, if the client interrupts his session, the results of the Crypto Helper uses the qke_continuation pointer which points to a recently freed memory area. The memory is thus corrupted by the result of the Crypto Helper.

When Openswan uses a Crypto Helper, a remote attacker can therefore interrupt an IKE session, in order to stop the pluto daemon.
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