Date: Wed, 05 Sep 2012 11:12:47 +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 17 (CVE-2012-3515) - Qemu VT100 emulation vulnerability -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2012-3515 / XSA-17 version 2 Qemu VT100 emulation vulnerability UPDATES IN VERSION 2 ==================== Public release. ISSUE DESCRIPTION ================= The device model used by fully virtualised (HVM) domains, qemu, does not properly handle escape VT100 sequences when emulating certain devices with a virtual console backend. IMPACT ====== An attacker who has sufficient privilege to access a vulnerable device within a guest can overwrite portions of the device model's address space. This can allow them to escalate their privileges to that of the device model process. VULNERABLE SYSTEMS ================== All Xen systems running HVM guests are potentially vulnerable to this depending on the specific guest configuration. The default configuration is vulnerable. Guests using either the traditional "qemu-xen" or upstream qemu device models are vulnerable. MITIGATION ========== This issue can be avoided by only running PV guests or by configuring HVM guests to not use the virtual console('vc') backend for any device. For serial devices specify in your guest configuration: serial = 'none' in your guest configuration. For parallel port devices the syntax is toolstack specific. For xend specify in your guest configuration: parallel = 'none' For xl specify in your guest configuration: xl: device_model_args = ['-parallel', 'none'] In both cases the default is to use the vulnerable 'vc' mode. You can confirm whether or not you are vulnerable by pressing Ctrl-Alt-<N> (for digit N) while connected to either the VNC or SDL console. If you are able to switch to a window displaying "serial" or "parallel" then you are vulnerable. The issue can also be mitigated by enabling the stub domain device model. In this case the attacked can only potentially gain control of the stub domain and not of the entire system. To enable stub domains specify in your guest configuration: device_model = "stubdom-dm" RESOLUTION ========== Applying the appropriate attached patch(es) will resolve the issue. PATCH INFORMATION ================= The attached patches resolve this issue Traditional qemu tree Xen 4.0, 4.1 and unstable xsa17-qemu-xen-traditional-all.patch Upstream qemu tree (present in unstable only) Xen unstable xsa17-qemu-xen-unstable.patch $ sha256sum xsa17-*.patch 60215322d3fbbc2054dfc160a20d9e0811af88487c4edc2f6ea81dcd5cedf039 xsa17-qemu-xen-traditional-all.patch 7b4bb59e7757080e7806a8b8eeb6b78fa0ffdfbfb28a7a379f7edff285bffd88 xsa17-qemu-xen-unstable.patch -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iQEcBAEBAgAGBQJQRx1PAAoJEIP+FMlX6CvZUqUH/jeAAvQnoBp6YKzm78XSnnmk GI2C/LhH0xqR3wFoEmWeMsiO4lrGrASX6T31NTvHa8sOtFqlNpTfRhwQybwYR3aa cz9/4y2a54hD95P1nVmPF0PddmSP47QSpRdCj0projq1UGxIdwEhkNeSoM8h7dXO MegqZClsvJMKd8XEcjBF5Qg7u9vLrXilCx5+It7XNE31Jxpkr/fozBb7FnNtDGJj s4RN/UDU4Pu68XyZ7Dc5xEFdJW48tz4BIlxxXavILBRFSE1VEf7Gc8H9CsUtBPWB C/LCUjpHkAOmqdgFhiLnZ2u+2s79U0dtPDJMNmqaGgWH+AqGkU9Nq8XXODTyY9k= =gnuE -----END PGP SIGNATURE----- Download attachment "xsa17-qemu-xen-traditional-all.patch" of type "application/octet-stream" (3537 bytes) Download attachment "xsa17-qemu-xen-unstable.patch" of type "application/octet-stream" (3537 bytes)
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