Xen Security Advisory CVE-2015-3456 / XSA-133 Privilege escalation via emulated floppy disk drive *** EMBARGOED UNTIL 2015-05-13 12:00 UTC *** ISSUE DESCRIPTION ================= The code in qemu which emulates a floppy disk controller did not correctly bounds check accesses to an array and therefore was vulnerable to a buffer overflow attack. IMPACT ====== A guest which has access to an emulated floppy device can exploit this vulnerability to take over the qemu process elevating its privilege to that of the qemu process. VULNERABLE SYSTEMS ================== All Xen systems running x86 HVM guests without stubdomains are 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. Guests using a qemu-dm stubdomain to run the device model are only vulnerable to takeover of that service domain. Systems running only x86 PV guests are not vulnerable. ARM systems are not vulnerable. MITIGATION ========== Enabling stubdomains will mitigate this issue, by reducing the escalation to only those privileges accorded to the service domain. qemu-dm stubdomains are only available with the traditional "qemu-xen" version. NOTE REGARDING EMBARGO ====================== The embargo was fixed by the discoverer, at the time the Xen Project Security Team and other response teams were notified (30th of April). Preparation of the patch involved coordination with upstream Qemu and drafting in of further help. The discoverer gave permission for the issue to be predisclosed today.
DEPLOYMENT DURING EMBARGO ========================= Deployment of the patches described above (or others which are substantially similar) is permitted during the embargo, even on public-facing systems with untrusted guest users and administrators. But: Deployment of the mitigation by enabling stubdomains is NOT permitted (except on systems used and administered only by organisations which are members of the Xen Project Security Issues Predisclosure List). Specifically, deployment on public cloud systems is NOT permitted. This is because this configuration change may be visible to the guest. Also, distribution of updated software is prohibited (except to other members of the predisclosure list). Predisclosure list members who wish to deploy significantly different patches and/or mitigations, please contact the Xen Project Security Team. (Note: this during-embargo deployment notice is retained in post-embargo publicly released Xen Project advisories, even though it is then no longer applicable. This is to enable the community to have oversight of the Xen Project Security Team's decisionmaking.) For more information about permissible uses of embargoed information, consult the Xen Project community's agreed Security Policy: http://www.xenproject.org/security-policy.html
*** Bug 549272 has been marked as a duplicate of this bug. ***
*** Bug 549384 has been marked as a duplicate of this bug. ***
Also affects QEMU, should this go into a separate bug report? Here's the patch: http://git.qemu.org/?p=qemu.git;a=commitdiff;h=e907746266721f305d67bc0718795fedee2e824c
(In reply to Hanno Boeck from comment #4) > Also affects QEMU, should this go into a separate bug report? Thanks. Yes, please file a new bug for this
in tree, fixed in following versions. app-emulation/xen-tools-4.2.5-r5 app-emulation/xen-tools-4.4.2-r2 app-emulation/xen-tools-4.5.0-r4
Arches, please test and mark stable: =app-emulation/xen-4.2.5-r9 =app-emulation/xen-tools-4.2.5-r5 Target keywords Both : "amd64 x86" =app-emulation/xen-4.4.2-r2 =app-emulation/xen-tools-4.4.2-r2 Target keywords Only: "amd64" (this also handle bug 547202)
amd64 stable
x86 stable. Maintainer(s), please cleanup. Security, please add it to the existing request, or file a new one.
New request filed together with bug 547202
old vulnerable versions have been dropped, thanks
CVE-2015-3456 (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2015-3456): The Floppy Disk Controller (FDC) in QEMU, as used in Xen 4.5.x and earlier and KVM, allows local guest users to cause a denial of service (out-of-bounds write and guest crash) or possibly execute arbitrary code via the (1) FD_CMD_READ_ID, (2) FD_CMD_DRIVE_SPECIFICATION_COMMAND, or other unspecified commands, aka VENOM.
This issue was resolved and addressed in GLSA 201604-03 at https://security.gentoo.org/glsa/201604-03 by GLSA coordinator Yury German (BlueKnight).
