12 November 2013
Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2013.1603 Xen Security Advisory XSA-75 12 November 2013 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Xen Publisher: Xen Operating System: Xen UNIX variants (UNIX, Linux, OSX) Impact/Access: Denial of Service -- Existing Account Resolution: Patch/Upgrade Original Bulletin: http://xenbits.xen.org/xsa/advisory-75.html - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory XSA-75 Host crash due to guest VMX instruction execution ISSUE DESCRIPTION ================= Permission checks on the emulation paths (intended for guests using nested virtualization) for VMLAUNCH and VMRESUME were deferred too much. The hypervisor would try to use internal state which is not set up unless nested virtualization is actually enabled for a guest. IMPACT ====== A malicious or misbehaved HVM guest, including malicious or misbehaved user mode code run in the guest, might be able to crash the host. VULNERABLE SYSTEMS ================== Xen 4.2.x and later are vulnerable. Xen 4.1.x and earlier are not vulnerable. Only HVM guests run on VMX capable (e.g. Intel) hardware can take advantage of this vulnerability. MITIGATION ========== Running only PV guests, or running HVM guests on SVM capable (e.g. AMD) hardware will avoid this issue. Enabling nested virtualization for a HVM guest running on VMX capable hardware would also allow avoiding the issue. However this functionality is still considered experimental, and is not covered by security support from the Xen Project security team. This approach is therefore not recommended for use in production. CREDITS ======= This issue was discovered by Jeff Zimmerman. NOTE REGARDING LACK OF EMBARGO ============================== This issue was disclosed publicly on the xen-devel mailing list. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa75-4.3-unstable.patch Xen 4.3.x, xen-unstable xsa75-4.2.patch Xen 4.2.x $ sha256sum xsa75*.patch 0b2da4ede6507713c75e313ba468b1fd7110e5696974ab72e2135f41ee393a8b xsa75-4.2.patch 91936421279fd2fa5321d9ed5a2b71fe76bc0e1348e67126e8b9cde0cb1d32b2 xsa75-4.3-unstable.patch $ - -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBAgAGBQJSfQ8xAAoJEIP+FMlX6CvZ8JQIAMc9IH79JeoZPAe/Fvz8TrdF FM7FkB/+sob4ybEFXnaSsK/7v7+A1e2qti/UVZfgcKEa8LG7aAIXFqsMXqErvME2 7D+r0Kt7QfvK5BvOygACCMsNV5muUTndVO8NUtHm8wDJk6yuSMWVnA/c3p+OSkH0 h63cfkrf9iYSYrPdCt4iO+/JKDVZl3bQAmHOFHvGTqsN7FMgOGexn+9RlNwWNmlU jvMxPLmwaerwd85fqLwEjajWT1TJlqro5xx4darKp8pokY+DVEtV4MGHXgllHVym t7g56Ph7YXPqTIJV4+PmrNQNwFPvsgBeFVyno3oa95IT4F55Fja0LiJUxREDHhU= =AbJ0 - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. 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On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBUoGbeRLndAQH1ShLAQKyuQ//YfEm60RT0wEw1pn4FLQl0or1SMQNDT4M 6fRfu3d9L/0ipIJrvkzVf0DJl1qIaWosidecEb+/HX5hj5O7LBp7E3EHteOwcpS7 hRIl5sPriefeYd/OhCifBJCLpc9fYglzByYMvae4cB2dBGWV2yyPQqh52SkJGEKL lF9HyehUKAaUwPG1cYZckUtK8lHfRXhlBJSmufj3tmx79HVpzlSFx8X6DktXCPBZ UwLgBPY0cBCVa93GU1kZwjDIgHD5UJfYSPXwUC0opSB44YJrNVt4x0E+ZRI9Yo84 9Wfsz+dMjjNtgmcWw4X7f7MGilZLQdb+MeFXRjPOioI6NzAaFho+5ipq8R8aea72 yL2Vm9IoA2tE0BQ4vESIzXbv9yjcH1vmcZdZCCP4MXIicOjC4PEtlrKwF85yPqQc HinEfQV1ilpKonzFwvwAFVzX7u59UKL0j0AcjVOOecTVkpZFjGwhv1zFGpc3+T9s kjSNjleeKgjBjJ8vGSnDa/48iFfcZV5KeSGr9bgQGZ2l+wWk9128Qjw4mvMuWkwo 1BkQAs4hOmstRS9ebNQql3+Aquy1hHqjqWHsn3wa7brBLHsCqVkcnvblVL1vuUoR c3MJkR2Kz9m/pT8Mr5sy/3qXPzpejRDsrS7nb13zXHXroW1e76tgp3zPoeQsRroC kvOU312PL50= =f3q8 -----END PGP SIGNATURE-----