#VU124683 Improper resource shutdown or release in FreeBSD - CVE-2026-4247
Published: March 30, 2026
Vulnerability identifier: #VU124683
Vulnerability risk: Medium
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-4247
CWE-ID: CWE-404
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
FreeBSD
FreeBSD
Software vendor:
FreeBSD Foundation
FreeBSD Foundation
Description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper memory management in the TCP stack when handling unexpected TCP segments that meet challenge ACK criteria. A remote attacker can send a specially crafted sequence of TCP packets to exceed the rate limit for challenge ACKs and trigger an mbuf leak, leading to resource exhaustion.
Off-path attackers may also exploit this issue by spoofing packets with guessed connection parameters, though this is more difficult.
Remediation
Install security update from vendor's website.