Citrix XenServer Multiple Vulnerabilities (CTX219378)
Medium Nessus Plugin ID 96778
SynopsisA server virtualization platform installed on the remote host is affected by multiple vulnerabilities.
DescriptionThe version of Citrix XenServer installed on the remote host is missing a security hotfix. It is, therefore, affected by multiple vulnerabilities :
- A flaw exists in x86 instruction CMPXCHG8B due to legacy operand size overrides not being properly ignored when handling prefixes. A guest attacker can exploit this to disclose potentially sensitive information on the host system. Note that the ability to read a small amount of hypervisor memory is restricted to privileged-mode code in all guests except on Citrix XenServer 6.2 SP1 and 6.0.2CC, where the attack may also be performed from non-privileged-mode code in HVM guest VMs.
- A denial of service vulnerability exists when a guest asynchronously modifies its instruction stream to effect the clearing of EFLAGS.IF. A guest attacker can exploit this to cause the host to hang or crash.
- A denial of service vulnerability exists due to a NULL pointer dereference flaw that is triggered when the hvmemul_vmfunc() function pointer uses inappropriate NULL checks before indirect function calls. A guest attacker can exploit this to cause the hypervisor to crash. Note that the ability of privileged-mode code in HVM guest VMs to crash the host is restricted to AMD systems running Citrix XenServer 7.0. (CVE-2016-10025)
SolutionApply the appropriate hotfix according to the vendor advisory.