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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2015.1319 Privilege escalation via emulated floppy disk drive 15 May 2015 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: qemu-xen Publisher: Xen Operating System: Xen Impact/Access: Execute Arbitrary Code/Commands -- Existing Account Denial of Service -- Existing Account Resolution: Patch/Upgrade CVE Names: CVE-2015-3456 Reference: ESB-2015.1308 ESB-2015.1307 ESB-2015.1306 ESB-2015.1304 Original Bulletin: http://xenbits.xenproject.org/xsa/advisory-133.html - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2015-3456 / XSA-133 version 2 Privilege escalation via emulated floppy disk drive UPDATES IN VERSION 2 ==================== Public release. 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. CREDITS ======= This issue was discovered by Jason Geffner, Senior Security Researcher at CrowdStrike. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa133-qemuu.patch qemu-upstream-unstable, Xen 4.5.x, Xen 4.4.x xsa133-qemuu-4.3-4.2.patch qemu-upstream-unstable, Xen 4.3.x, Xen 4.2.x xsa133-qemut.patch qemu-xen-unstable, Xen 4.5.x, Xen 4.4.x, Xen 4.3.x, Xen 4.2.x $ sha256sum xsa133*.patch e7ca0106a9d4bfe472b3b52bbed8646b47305634ff16c3e17ed6185296a7e7ff xsa133-qemut.patch 0cbc0415ef63bc195a0338441f3770d9fe6741e894879e35d1a6609ad028e42f xsa133-qemuu.patch cf735c1ecb6a40ca57d408e5c01725eca5b9b0a14b1d31b4362dc3f036bdeb28 xsa133-qemuu-4.3-4.2.patch $ 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 - -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBAgAGBQJVUzJdAAoJEIP+FMlX6CvZnJcH/iszFBI+ltmOGxfCtSmnnkdu 6GZUFCVimeVG2ZfDCe1Bvw63ZMeB8AMUr2KmFrg0pOfC7m1Mc/4UhczpqeY9G1i0 kPCcNiK37Ju0otFN1AODHaYGhu6pgfTM+QV1muFVXHf9QibmH+vEy7HEN34Mtv/2 gGRmxLJnkHFME2sISuqhDsxIMf5QWN28I412/QqK8/mJMuvCJHqbLs/fv9f0uj9g sgAVCb3gsqNS7SSK1v49PqK+lQV+BkPR8pi8ODdL301iZWfu8PbVpYa5A84LVQF0 4ZnlVfWqeKXF7GlsuviinhQIoUIvSktf9tg65fM48Thk0UUp+MyHVkh4GkT/+Eo= =rN8t - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBVVVLuhLndAQH1ShLAQJFVxAAu+ZHQrrNvP6R9fWTCOCsgnwuxFay1wOz xPu5Wm76qHC38ttiG7g3lwTfaea0YJ9uuI3bMWJZeCfsYCZkYFnf3/CujOH7DEXh S8wckAEwVbbIpknA27vtSZ+48ax/N1OUIesSrsIFyzMubIrTOVIVxuiBNlXdtrdf s63FGlJV9i5AfCl7VX18KVGywolQjk+0nrkVBVaApBGma1gqMUAzKvMf/+/Z2f94 msFdy/ud5mPKjzCekV2t9IqcA75wnnMtsKXvGNYoFaqYQt36CtCZhlBIBJeDAf9d TjLLqkac8y7H4jfV+t7Lgpzk+ShTrllt0gE87Sa+VGcFPHrrZJJJYme6nG78s+dv iSSVBkmKPOF+VumYTpG2qRc2KoXtbodtbE6aA8nOZoUDWUXlTvqMrYLSpGIljO7/ GCh0wTd5h1WKeixP6+djTsY4Cf1RzbNRAvFPDZIxLId37CoNzZhIr5BFRh7ZvRHt 7PuzjkOANTm9wPifVQiQV3/ET1p3WCsdX+Jn7/ria9SO7bpxmketiDVMc2889Epx JTt0ztq2/lEAIBXwGo2ojMlFfcKX6WjXmsbEk0/+7xfq7dcGur1O04LLFZrfWhyR v+As4IYU6DR7mtxa7+ZQS0JOJsX1iK0TciqLtjb6dK0xa9Om0V+2sFal83pUE03M 4fn/fnDzC3M= =+UE/ -----END PGP SIGNATURE-----