CVE-2011-4539

CVE-2011-4539 is a medium-severity vulnerability in Isc Dhcp with a CVSS 2.0 base score of 5.0. Its EPSS exploit-prediction score of 15% places it in the 96th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-20.

Key facts

• Severity: Medium (CVSS 2.0 base score 5.0)
• EPSS exploit prediction: 15% (96th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-20
• Affected product: Isc Dhcp
• Published: 2011-12-08
• Last modified: 2026-06-16

Description

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 expressions in dhcpd.conf, which allows remote attackers to cause a denial of service (daemon crash) via a crafted request packet.

Frequently asked questions

What is 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 expressions in dhcpd.conf, which allows remote attackers to cause a denial of service (daemon crash) via a crafted request packet.

How severe is CVE-2011-4539?

CVE-2011-4539 has a CVSS 2.0 base score of 5.0, rated medium severity.

Is CVE-2011-4539 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 15% (96th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2011-4539?

CVE-2011-4539 primarily affects Isc Dhcp. In total, 39 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2011-4539?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2011-4539 published?

CVE-2011-4539 was published on 2011-12-08 and last updated on 2026-06-16.

References

• http://lists.fedoraproject.org/pipermail/package-announce/2011-December/070980.html
• http://lists.fedoraproject.org/pipermail/package-announce/2012-January/071549.html
• http://lists.opensuse.org/opensuse-updates/2011-12/msg00006.html
• http://secunia.com/advisories/47153
• http://secunia.com/advisories/47178
• http://security.gentoo.org/glsa/glsa-201301-06.xml
• http://www.debian.org/security/2012/dsa-2519
• http://www.mandriva.com/security/advisories?name=MDVSA-2011:182
• http://www.securityfocus.com/bid/50971
• http://www.securitytracker.com/id?1026393
• http://www.ubuntu.com/usn/USN-1309-1
• https://exchange.xforce.ibmcloud.com/vulnerabilities/71680
• https://www.isc.org/software/dhcp/advisories/cve-2011-4539

Affected products (39)

• cpe:2.3:a:isc:dhcp:4.0:*:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.0:*:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.1:-:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.1:b1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.1:rc1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.2:-:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.2:b1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.2:b2:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.2:b3:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.2:rc1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.3:-:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.3:b1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.0.3:rc1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.1.1:b3:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.1.1:rc1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.1.2:*:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.0:-:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.0:a1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.0:a2:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.0:b1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.0:b2:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.0:p1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.0:rc1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.1:-:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.1:b1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.1:rc1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.2:-:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.2:b1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.2:rc1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.2.3:-:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.1-esv:-:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.1-esv:r1:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.1-esv:r2:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.1-esv:r3:*:*:*:*:*:*
• cpe:2.3:a:isc:dhcp:4.1-esv:r3_b1:*:*:*:*:*:*
• cpe:2.3:o:canonical:ubuntu_linux:11.04:*:*:*:*:*:*:*
• cpe:2.3:o:canonical:ubuntu_linux:11.10:*:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:6.0:*:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:7.0:*:*:*:*:*:*:*

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• CVE-2011-2748 — High (CVSS 7.8): The server in ISC DHCP 3.x and 4.x before 4.2.2, 3.1-ESV before 3.1-ESV-R3, and 4.1-ESV before 4.1-ESV-R3 allows remote…
• CVE-2011-0413 — High (CVSS 7.8): The DHCPv6 server in ISC DHCP 4.0.x and 4.1.x before 4.1.2-P1, 4.0-ESV and 4.1-ESV before 4.1-ESV-R1, and 4.2.x before…
• CVE-2018-5732 — High (CVSS 7.5): Failure to properly bounds-check a buffer used for processing DHCP options allows a malicious server (or an entity…
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