Description
The RACK setsockopt(2) handler drops the connection lock in order to copy option data from userspace, then reacquires the lock. After reacquiring, it verifies that the TCP stack had not been switched away, but did not reload its pointer to the stack's per-connection control block. If userspace switches stacks twice during this window, the check will succeed but the saved pointer will refer to freed memory.

The bug may be exploitable by an unprivileged local user to escalate privileges.
Published: 2026-08-19
Score: n/a
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Wed, 19 Aug 2026 05:45:00 +0000

Type Values Removed Values Added
Description The RACK setsockopt(2) handler drops the connection lock in order to copy option data from userspace, then reacquires the lock. After reacquiring, it verifies that the TCP stack had not been switched away, but did not reload its pointer to the stack's per-connection control block. If userspace switches stacks twice during this window, the check will succeed but the saved pointer will refer to freed memory. The bug may be exploitable by an unprivileged local user to escalate privileges.
Title Use-after-free in TCP RACK stack option handler
Weaknesses CWE-416
References

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cve-icon MITRE

Status: PUBLISHED

Assigner: freebsd

Published:

Updated: 2026-08-19T05:28:32.468Z

Reserved: 2026-05-29T20:24:28.616Z

Link: CVE-2026-49422

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-19T06:17:41.447

Modified: 2026-08-19T06:17:41.447

Link: CVE-2026-49422

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-19T06:30:05Z

Weaknesses