Vulnerability Details CVE-2020-25603
An issue was discovered in Xen through 4.14.x. There are missing memory barriers when accessing/allocating an event channel. Event channels control structures can be accessed lockless as long as the port is considered to be valid. Such a sequence is missing an appropriate memory barrier (e.g., smp_*mb()) to prevent both the compiler and CPU from re-ordering access. A malicious guest may be able to cause a hypervisor crash resulting in a Denial of Service (DoS). Information leak and privilege escalation cannot be excluded. Systems running all versions of Xen are affected. Whether a system is vulnerable will depend on the CPU and compiler used to build Xen. For all systems, the presence and the scope of the vulnerability depend on the precise re-ordering performed by the compiler used to build Xen. We have not been able to survey compilers; consequently we cannot say which compiler(s) might produce vulnerable code (with which code generation options). GCC documentation clearly suggests that re-ordering is possible. Arm systems will also be vulnerable if the CPU is able to re-order memory access. Please consult your CPU vendor. x86 systems are only vulnerable if a compiler performs re-ordering.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.001
EPSS Ranking 19.8%
CVSS Severity
CVSS v3 Score 7.8
CVSS v2 Score 4.6
Products affected by CVE-2020-25603
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cpe:2.3:o:debian:debian_linux:10.0
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cpe:2.3:o:fedoraproject:fedora:31
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cpe:2.3:o:fedoraproject:fedora:32
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cpe:2.3:o:fedoraproject:fedora:33
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cpe:2.3:o:opensuse:leap:15.2
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cpe:2.3:o:xen:xen:4.1.6.1
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