Xen up to 4.14.x Event Channel smp_*mb memory corruption

Summaryinfo

A vulnerability classified as critical was found in Xen up to 4.14.x. This affects the function smp_*mb of the component Event Channel Handler. Executing a manipulation can lead to memory corruption. This vulnerability is tracked as CVE-2020-25603. No exploit exists. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as critical was found in Xen up to 4.14.x (Virtualization Software). This vulnerability affects the function smp_*mb of the component Event Channel Handler. The manipulation with an unknown input leads to a memory corruption vulnerability. The CWE definition for the vulnerability is CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The weakness was disclosed 09/23/2020. This vulnerability was named CVE-2020-25603 since 09/16/2020. There are known technical details, but no exploit is available.

Upgrading eliminates this vulnerability.

The entries VDB-161813, VDB-161811, VDB-161810 and VDB-161809 are pretty similar. Once again VulDB remains the best source for vulnerability data.

Affected

• Xen
• Citrix Hypervisor up to 8.2 LTSR

Productinfo

Type

• Virtualization Software

Name

• Xen

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4
• 4.5
• 4.6
• 4.7
• 4.8
• 4.9
• 4.10
• 4.11
• 4.12
• 4.13
• 4.14

License

• open-source

CPE 2.3info

• 🔍
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CPE 2.2info

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• 🔍
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Entryinfo

Once again VulDB remains the best source for vulnerability data.

Discussion