Date: Tue, 07 Jul 2015 12:26:11 +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 137 (CVE-2015-3259) - xl command line config handling stack overflow -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2015-3259 / XSA-137 version 3 xl command line config handling stack overflow UPDATES IN VERSION 3 ==================== Public release. ISSUE DESCRIPTION ================= The xl command line utility mishandles long configuration values when passed as command line arguments, with a buffer overrun. VULNERABLE SYSTEMS ================== Systems built on top of xl which pass laundered or checked (but otherwise untrusted) configuration values onto xl's command line, without restricting their length, are vulnerable. We are not presently aware of any publicly distributed production software which exposes the xl vulnerability. However it is sufficiently simple to create such an arrangement that it might be done locally in an attempt to grant partial management access to particular domains. Systems using the libxl library directly, without using xl, are not vulnerable. Systems using toolstacks other than xl are not vulnerable. Systems where only fully trusted input is ever presented to the xl command line are not vulnerable. The vulnerability exists on x86 and ARM. The vulnerability was introduced in Xen 4.1 and affects all subsequent Xen releases. IMPACT ====== A semi-trusted guest administrator or controller, who is intended to be able to partially control the configuration settings for a domain, can escalate their privileges to that of the whole host. MITIGATION ========== Limiting the length of untrusted configuration settings will avoid the vulnerability. (The total length of all command-line configuration settings, including some interposed newlines and trailing nul, must be less than 1024.) CREDITS ======= This issue was discovered by Donghai Zhu of Alibab. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa137.patch Xen 4.2.x and later $ sha256sum xsa137*.patch 0272c443575c88b53445c89ef84f0cd98a03944d3303f06c66c33ef0037d97b9 xsa137.patch $ DEPLOYMENT DURING EMBARGO ========================= Deployment of the patches and/or mitigations 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: 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) iQEcBAEBAgAGBQJVm8UeAAoJEIP+FMlX6CvZmnEH/1Tq+nP7STM4yE56JJsqUikV HmKbJuCy6yApsMQ7JrPjbs3yo826OQl3BVyZBicfgk6B2Cx78QgbF+XGK6B/9sfz DP5bMwz9S4n5u7K4bMkppx+6p2nG06hkzfdwzGbCC3nKiW9chYo4NdPtcQRA4d2d LnSN7JGJjxAFq22a3KKlb5AILr6x/+PYPan/jolf39rXmU1Lcg0fsMFuLm8fK1MQ burOoCphm8Xd0UOgNaH2BGCAjYoFuxKC7n12u9poCFQpnyKsYI7YGvLI2X6NgHOZ PRRSsuWqf0g7huzM/UkvPthCJzxmPWPqrLoBVOuspAOFVcqwqDmdKKSjcppEV+Q= =rvRm -----END PGP SIGNATURE----- Download attachment "xsa137.patch" of type "application/octet-stream" (8132 bytes)
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