Date: Mon, 30 Sep 2013 12:04:25 +0000 From: Xen.org security team <security@....org> To: xen-announce@...ts.xen.org, xen-devel@...ts.xen.org, xen-users@...ts.xen.org, oss-security@...ts.openwall.com CC: Xen.org security team <security@....org> Subject: Xen Security Advisory 66 (CVE-2013-4361) - Information leak through fbld instruction emulation -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2013-4361 / XSA-66 version 3 Information leak through fbld instruction emulation UPDATES IN VERSION 3 ==================== Public Release. ISSUE DESCRIPTION ================= The emulation of the fbld instruction (which is used during I/O emulation) uses the wrong variable for the source effective address. As a result, the actual address used is an uninitialised bit pattern from the stack. A malicious guest might be able to find out information about the contents of the hypervisor stack, by observing which values are actually being used by fbld and inferring what the address must have been. Depending on the actual values on the stack this attack might be very difficult to carry out. IMPACT ====== A malicious guest might conceivably gain access to sensitive data relating to other guests. VULNERABLE SYSTEMS ================== Xen 3.3.x and later are vulnerable. Only HVM guests can take advantage of this vulnerability. MITIGATION ========== Running only PV guests will avoid this issue. There is no mitigation available for HVM guests. We believe this vulnerability would require significant research to exploit. CREDITS ======= Jan Beulich discovered this issue. RESOLUTION ========== Applying the attached patch resolves this issue. xsa66.patch Xen 4.2.x, Xen 4.3.x, xen-unstable $ sha256sum xsa66.patch 3a9b6bf114eb19d708b68dd5973763ac83b57840bc0f6fbd1fe487797eaffed4 xsa66.patch $ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBAgAGBQJSSUhOAAoJEIP+FMlX6CvZdTsIAISzxoVv5PVKcT3RlikuDPdS AN4b5d/AJHGUcVg0K8CAd5UpvP0y5UfVhMFc+LCNDoeTE6a+4PsS/2V49HX259tT oX1HDZUxzfDbNTgZL5/hS3RUNZvTlWxVS0E5SMRW5jDrScPFUOqliD9hNj2cyvlq Ne362V5VFFb9AcZsMPnl2V4FerUyyuTCncxcvsvDshFIhBaqBY8G/LBqIHE7CKZF qCK9688RIMlwgNag7fbSloCLOifC7Jrfp9k+wfhAUdLj6R6l2SuyItYa7KufTAof /bWddQVFxhxcapYMDiNExZNxbHoM51rAeSkC3eYn6BGWKjqfIetA4X+uzfP3LNc= =PSEF -----END PGP SIGNATURE----- Download attachment "xsa66.patch" of type "application/octet-stream" (839 bytes)
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