Improper Neutralization of Special Elements in Output Used by a Downstream Component in FreeBSD - CVE-2026-42511
Published: April 30, 2026
Vulnerability identifier: #VU128484
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-42511
CWE-ID: CWE-74
Exploitation vector: Adjecent network
Exploit availability:
No public exploit available
Vendor: FreeBSD Foundation
Affected software:
FreeBSD
FreeBSD
Detailed vulnerability description
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to improper neutralization of special elements in the lease file handling in dhclient when processing malicious DHCP options from a rogue DHCP server on the same broadcast domain. A remote attacker can send crafted DHCP responses containing a BOOTP file field with embedded double-quotes to execute arbitrary code.
Code execution occurs when the lease file is later re-parsed, such as after a system restart, and attacker-controlled content is passed to dhclient-script(8) for evaluation.
How to mitigate CVE-2026-42511
Install security update from vendor's website.