CVE-2011-4539: dhcpd in ISC DHCP 4.x before 4.2.3-P1 and 4.1-ESV before 4.1-ESV-R4 does not properly handle regular expres...

Security readout for executives and security teams

This CVE can let a remote attacker crash ISC DHCP's dhcpd service by sending a crafted DHCP request. The business impact is availability: affected DHCP servers may stop assigning or renewing network addresses, disrupting users and systems that depend on DHCP. Exposure is most likely on networks running ISC DHCP dhcpd 4.x before the fixed releases, especially where dhcpd.conf uses regular expressions. Internet exposure is less typical for DHCP, but internal or adjacent network attackers may be relevant. Treat as a service availability issue. Patch affected DHCP servers during the next urgent maintenance window, sooner for critical network segments where DHCP outage would disrupt operations. Mitigation focus: Upgrade ISC DHCP to 4.2.3-P1, 4.1-ESV-R4, or later supported packages.; Apply relevant OS vendor security updates from Ubuntu, Debian, Fedora, openSUSE, Mandriva, or Gentoo.; Check ISC and distribution advisories for platform-specific remediation guidance..

Prepared

Jun 27, 2026, 17:48 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.