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.

• CVE ID
• CVE-2020-25603

• Assigner
• cve@mitre.org

• Vulnerability Status
• Analyzed

• Published Version
• 2020-09-23T22:15:13

• Last Modified Date
• 2022-04-28T18:19:44

• Version
• 2.0

• Vector String
• AV:L/AC:L/Au:N/C:P/I:P/A:P

• Access Vector
• LOCAL

• Access Compatibility
• LOW

• Authentication
• NONE

• Confidentiality Impact
• PARTIAL

• Integrity Impact
• PARTIAL

• Availability Impact
• PARTIAL

• Base Score
• 4.6

• Severity
• MEDIUM

• Exploitability Score
• 3.9

• Impact Score
• 6.4

• Version
• 3.1

• Vector String
• CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

• Attack Vector
• LOCAL

• Attack Compatibility
• LOW

• Privileges Required
• LOW

• User Interaction
• NONE

• Scope
• UNCHANGED

• Confidentiality Impact
• HIGH

• Availability Impact
• HIGH

• Base Score
• 7.8

• Base Severity
• HIGH

• Exploitability Score
• 1.8

• Impact Score
• 5.9