-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory CVE-2015-3259 / XSA-137 version 4 xl command line config handling stack overflow UPDATES IN VERSION 4 ==================== Correct reference to `Alibaba' in CREDITS. Normalize version tags. 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 Alibaba. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa137.patch xen-unstable - Xen 4.2.x $ 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----- iQFABAEBCAAqFiEEI+MiLBRfRHX6gGCng/4UyVfoK9kFAmV8b+4MHHBncEB4ZW4u b3JnAAoJEIP+FMlX6CvZ/XIIALJUpPdHo5HAe4OqjfRwQazW46uwLF8kzx/mQfF1 lJE0M9dVHx/8uiR+LsXr2DRrfZWlAMUmebcGzKoBXsbQFBD3h3D1xVIFwxZzxC6d mEq6Cn/iU3XEk77YMWcRGYpglvWD12C8BC/wH+EYkcpppDsowEi0VKwm9vvW1/5i kjnq1k71r5wERqTIAZbaSk1dL2UWt1NRixc2YGPAc/3Gy/TEC3fnbGtc477/VVNd I2IlQec8vOQJ2hJRxgwdb4OYOMzd+3jFl00CEjCa1aXIz6CYu5qDyFlEngvM8IEp KEnAcMx0wWK2YC99QCf0RRmDsDmUVklFNCw8Jt+1ekTDVwU= =m9jc -----END PGP SIGNATURE-----