CVE-2026-101307 FreeBSD CVE debrief

Who should care

System administrators and security teams responsible for FreeBSD systems should assess their exposure and take necessary mitigation steps. This includes reviewing and applying patches, restricting access to the affected system, and monitoring for suspicious network activity. Security teams should also verify the affected scope and severity with the vendor advisory and plan vendor-supported updates or mitigations through normal change control where exposure

Why it matters

A remotely triggerable buffer overflow vulnerability exists in the tcp_rack stack of FreeBSD, potentially resulting in a kernel panic. System administrators and security teams should assess their exposure and take necessary mitigation steps.

• Remote attackers may be able to trigger a kernel panic, leading to system instability.
• Successful exploitation requires establishing a TCP connection to the affected system.
• The vulnerability can be triggered by sending a sufficient number of ACKs on an established connection.
• The impact of a kernel panic may require system reboot and potential data loss.

Technical summary

The vulnerability exists in the tcp_rack stack of FreeBSD, where a remote attacker can trigger an out-of-bounds write of approximately 512 KB in the kernel heap, potentially resulting in a kernel panic. The issue arises from repeated doublings of a 16-bit allocation counter, causing it to wrap to zero, and a subsequent copy of existing samples into the undersized buffer. The vulnerability can be triggered by sending a sufficient number of ACKs on an established connection, and system administrators should assess their exposure and take necessary mitigation steps.

Defensive priority

High

Recommended defensive actions

• Review and apply patches from the vendor
• Restrict access to the affected system
• Monitor for suspicious network activity
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.
• Review compensating controls for exposed systems while remediation is scheduled and verified.

Evidence notes

The vulnerability is described in the CVE Program record and the NVD vulnerability detail page. The FreeBSD advisory provides additional information on the affected versions and mitigation strategies. Evidence limits are based on available source information, and defenders should verify the affected scope and severity with the vendor advisory.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.