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CVE-2026-101308 FreeBSD CVE debrief

A TOCTOU race condition exists in the sound(4) driver of FreeBSD, allowing an unprivileged local user to trigger a use-after-free in the kernel, potentially escalating privileges. The issue arises when an audio channel's buffer needs to be resized, and the sound(4) driver checks that the buffer is not memory-mapped before dropping the channel lock to allocate a new buffer. During this window, an mmap(2) call on another thread can complete, after which the resize path frees the now-mapped buffer without rechecking.

Vendor
FreeBSD
Product
Unknown
CVSS
Unknown
CISA KEV
Not listed in stored evidence
Original CVE published
2026-10-15
Original CVE updated
2026-10-15
Advisory published
2026-10-15
Advisory updated
2026-10-15

Who should care

System administrators and security teams responsible for FreeBSD systems, particularly those with unprivileged local users, should assess exposure and apply the vendor-provided patch.

Why it matters

The TOCTOU race condition in the FreeBSD sound(4) driver allows unprivileged local users to potentially escalate privileges, making it crucial for system administrators and security teams to assess exposure and apply patches.

  • Potential privilege escalation for unprivileged local users.
  • Possible system instability or crashes due to use-after-free errors.
  • Need for verification of affected FreeBSD versions and application of patches.
  • Importance of monitoring system logs for exploitation attempts.

Technical summary

The sound(4) driver in FreeBSD is vulnerable to a TOCTOU (Time-of-Check-to-Time-of-Use) race condition. When an audio channel's buffer needs to be resized, the driver checks that the buffer is not memory-mapped and then drops the channel lock to allocate a new buffer. An mmap(2) call on another thread can complete during this window, allowing an unprivileged local user to trigger a use-after-free in the kernel, potentially escalating privileges.

Defensive priority

High

Recommended defensive actions

  • Review and apply the vendor-provided patch for the sound(4) driver.
  • Restrict access to sound devices for unprivileged local users.
  • Monitor system logs for potential exploitation attempts.
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
  • Review compensating controls for exposed systems while remediation is scheduled and verified.
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review.
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The CVE record and source item provide details on the TOCTOU race condition in the sound(4) driver of FreeBSD. The FreeBSD advisory (FreeBSD-SA-26:71.sound.asc) is referenced as a source reference. Evidence is limited to public CVE details and a FreeBSD advisory. Defenders should verify affected FreeBSD versions, review system logs for exploitation attempts, and apply the vendor-provided patch. Limited public information exists on exploitation or scope; further verification is necessary.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-101308 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-101308

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-101308 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-101308

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • TOCTOU race between sound(4) buffer resizing and mmap

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/101xxx/CVE-2026-101308.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://security.freebsd.org/advisories/FreeBSD-SA-26:71.sound.asc

    Supplemental source - vendor-advisory

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.