Use-after-free in FreeBSD - CVE-2026-49422
Published: July 1, 2026
Vulnerability identifier: #VU136013
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-49422
CWE-ID: CWE-416
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vendor: FreeBSD Foundation
Affected software:
FreeBSD
FreeBSD
Detailed vulnerability description
The vulnerability allows a local user to escalate privileges.
The vulnerability exists due to use-after-free in the TCP RACK setsockopt(2) handler when copying option data from userspace while the TCP stack is switched twice during a lock drop window. A local user can switch TCP stacks twice during this window to escalate privileges.
Only systems with the tcp_rack.ko kernel module loaded are vulnerable.
How to mitigate CVE-2026-49422
Install security update from vendor's website.