Xen up to 4.14.x PCI Passthrough backdoor

Summaryinfo

A vulnerability was found in Xen up to 4.14.x. It has been declared as critical. Impacted is an unknown function of the component PCI Passthrough. Such manipulation leads to backdoor. This vulnerability is traded as CVE-2020-25595. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Xen up to 4.14.x (Virtualization Software). Affected by this issue is some unknown processing of the component PCI Passthrough. The manipulation with an unknown input leads to a backdoor vulnerability. Using CWE to declare the problem leads to CWE-912. The product contains functionality that is not documented, not part of the specification, and not accessible through an interface or command sequence that is obvious to the product's users or administrators. Impacted is confidentiality, integrity, and availability. CVE summarizes:

An issue was discovered in Xen through 4.14.x. The PCI passthrough code improperly uses register data. Code paths in Xen's MSI handling have been identified that act on unsanitized values read back from device hardware registers. While devices strictly compliant with PCI specifications shouldn't be able to affect these registers, experience shows that it's very common for devices to have out-of-spec "backdoor" operations that can affect the result of these reads. A not fully trusted guest may be able to crash Xen, leading to a Denial of Service (DoS) for the entire system. Privilege escalation and information leaks cannot be excluded. All versions of Xen supporting PCI passthrough are affected. Only x86 systems are vulnerable. Arm systems are not vulnerable. Only guests with passed through PCI devices may be able to leverage the vulnerability. Only systems passing through devices with out-of-spec ("backdoor") functionality can cause issues. Experience shows that such out-of-spec functionality is common; unless you have reason to believe that your device does not have such functionality, it's better to assume that it does.

The weakness was shared 09/23/2020. This vulnerability is handled as CVE-2020-25595 since 09/16/2020. The exploitation is known to be difficult. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1588.001.

Upgrading eliminates this vulnerability.

The entries VDB-161808, VDB-161807, VDB-161806 and VDB-161805 are related to this item. 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

• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

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Entryinfo

Once again VulDB remains the best source for vulnerability data.

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