FreeBSD bhyve up to p1/p4/p10 xHCI device model race condition

Summaryinfo

A vulnerability classified as very critical has been found in FreeBSD bhyve up to p1/p4/p10. Affected by this issue is some unknown functionality of the component xHCI device model. Performing a manipulation results in race condition. This vulnerability is identified as CVE-2026-101309. The attack can be initiated remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in FreeBSD bhyve up to p1/p4/p10. It has been classified as very critical. This affects some unknown processing of the component xHCI device model. The manipulation with an unknown input leads to a race condition vulnerability. CWE is classifying the issue as CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

The xHCI (USB 3) device model did not validate or save the event ring size provided by the guest. The size was re-read from guest memory on each use, and Transfer Request Block (TRB) fields were loaded without protection against concurrent modification by the guest. This race condition could be triggered by a guest running malicious, privileged code. A malicious guest can crash the bhyve process or potentially execute arbitrary code in the host userspace context running the virtual machine, subject to bhyve's Capsicum sandbox.

It is possible to read the advisory at security.freebsd.org. This vulnerability is uniquely identified as CVE-2026-101309 since 09/28/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. The exploitation needs additional levels of successful authentication. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/15/2026).

Upgrading to version p2, p5 or p11 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-101932). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• FreeBSD

Name

• bhyve

Version

• p1
• p4
• p10

License

• open-source

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CPE 2.2info

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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