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CVE Record

CVE-2020-25596: An issue was discovered in Xen through 4.14.x.

An issue was discovered in Xen through 4.14.x. x86 PV guest kernels can experience denial of service via SYSENTER. The SYSENTER instruction leaves various state sanitization activities to software. One of Xen's sanitization paths injects a #GP fault, and incorrectly delivers it twice to the guest. This causes the guest kernel to observe a kernel-privilege #GP fault (typically fatal) rather than a user-privilege #GP fault (usually converted into SIGSEGV/etc.). Malicious or buggy userspace can crash the guest kernel, resulting in a VM Denial of Service. All versions of Xen from 3.2 onwards are vulnerable. Only x86 systems are vulnerable. ARM platforms are not vulnerable. Only x86 systems that support the SYSENTER instruction in 64bit mode are vulnerable. This is believed to be Intel, Centaur, and Shanghai CPUs. AMD and Hygon CPUs are not believed to be vulnerable. Only x86 PV guests can exploit the vulnerability. x86 PVH / HVM guests cannot exploit the vulnerability.

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Glexia's TakeAutomated analysis

Security readout for executives and security teams

This Xen flaw lets malicious or faulty code inside an affected paravirtualized guest crash that guest’s kernel. The practical business impact is virtual machine denial of service, not documented host compromise. Exposure is narrow: x86 Xen PV guests on certain CPU families; ARM, AMD, Hygon, PVH, and HVM guests are described as not vulnerable. Highest exposure is infrastructure running Xen x86 PV guests on CPUs believed affected: Intel, Centaur, and Shanghai. Systems using ARM, AMD, Hygon, x86 PVH, or x86 HVM are described as not exploitable by this issue. Confirm against vendor advisories because package-level fixed versions are not provided in the source bundle. Treat this as a targeted availability risk for Xen virtualization estates, especially service providers or internal platforms relying on PV guests. It warrants normal urgent patch management where affected, but the sources do not support emergency treatment for environments without x86 PV guests or affected CPUs. Mitigation focus: Apply Xen or distribution security updates from the relevant vendor advisory.; Prioritize hosts running x86 PV guests on affected CPU families.; Where operationally supported, migrate exposed PV guests to PVH or HVM..

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Unknown
CVSS
Not scored
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CNA and ADP enrichment extracted from CVE v5

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