What is the CVSS score of CVE-2020-25597?

CVE-2020-25597 has a CVSS 3.1 base score of 6.5 (Medium). CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H. EPSS exploitation probability: 0.4%.

Is there a patch available for CVE-2020-25597?

Yes, a patch is available for CVE-2020-25597. Update the affected software to the latest version immediately.

Xen CVE-2020-25597

MEDIUM

Improper Handling of Exceptional Conditions (CWE-755)

2020-09-23 cve@mitre.org

Denial Of Service Xen Fedora

6.5

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

6.5 MEDIUM

AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Changed

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

CVE Published

Sep 23, 2020 - 22:15 nvd

MEDIUM 6.5

DescriptionNVD

An issue was discovered in Xen through 4.14.x. There is mishandling of the constraint that once-valid event channels may not turn invalid. Logic in the handling of event channel operations in Xen assumes that an event channel, once valid, will not become invalid over the life time of a guest. However, operations like the resetting of all event channels may involve decreasing one of the bounds checked when determining validity. This may lead to bug checks triggering, crashing the host. An unprivileged guest may be able to crash Xen, leading to a Denial of Service (DoS) for the entire system. All Xen versions from 4.4 onwards are vulnerable. Xen versions 4.3 and earlier are not vulnerable. Only systems with untrusted guests permitted to create more than the default number of event channels are vulnerable. This number depends on the architecture and type of guest. For 32-bit x86 PV guests, this is 1023; for 64-bit x86 PV guests, and for all ARM guests, this number is 4095. Systems where untrusted guests are limited to fewer than this number are not vulnerable. Note that xl and libxl limit max_event_channels to 1023 by default, so systems using exclusively xl, libvirt+libxl, or their own toolstack based on libxl, and not explicitly setting max_event_channels, are not vulnerable.

AnalysisAI

An issue was discovered in Xen through 4.14.x. Rated medium severity (CVSS 6.5), this vulnerability is low attack complexity.

Technical ContextAI

This vulnerability is classified under CWE-755. An issue was discovered in Xen through 4.14.x. There is mishandling of the constraint that once-valid event channels may not turn invalid. Logic in the handling of event channel operations in Xen assumes that an event channel, once valid, will not become invalid over the life time of a guest. However, operations like the resetting of all event channels may involve decreasing one of the bounds checked when determining validity. This may lead to bug checks triggering, crashing the host. An unprivileged guest may be able to crash Xen, leading to a Denial of Service (DoS) for the entire system. All Xen versions from 4.4 onwards are vulnerable. Xen versions 4.3 and earlier are not vulnerable. Only systems with untrusted guests permitted to create more than the default number of event channels are vulnerable. This number depends on the architecture and type of guest. For 32-bit x86 PV guests, this is 1023; for 64-bit x86 PV guests, and for all ARM guests, this number is 4095. Systems where untrusted guests are limited to fewer than this number are not vulnerable. Note that xl and libxl limit max_event_channels to 1023 by default, so systems using exclusively xl, libvirt+libxl, or their own toolstack based on libxl, and not explicitly setting max_event_channels, are not vulnerable. Affected products include: Xen, Fedoraproject Fedora. Version information: through 4.14..

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.