CVE-2020-37127: 
dnsmasq vulnerability analysis and mitigation

CVE-2020-37127 is a stack-based buffer overflow vulnerability in the dhcp_release utility included with dnsmasq-utils version 2.79-1. The flaw allows attackers to cause a denial of service by supplying an input string longer than 16 characters, triggering a core dump and terminating the dhcp_release process. It was formally published on February 5, 2026, and carries a CVSS v3.1 base score of 5.5 (Medium) (Red Hat Advisory, Red Hat Bugzilla).

The root cause is a classic buffer overflow (CWE-120 / CWE-121: Stack-based Buffer Overflow) in the dhcp_release utility, which fails to validate the length of user-supplied input before copying it into a fixed-size stack buffer of 16 characters. An attacker who can invoke dhcp_release with a crafted argument exceeding this limit will overflow the stack buffer, causing the process to crash. The attack vector is local (AV:L), requires no privileges (PR:N), but does require user interaction (UI:R) under the CVSS v3.1 scoring (Red Hat Advisory, VulnCheck Advisory). A public proof-of-concept exploit is listed on Exploit-DB (EDB-48301) (EUVD).

Successful exploitation results in a denial of service: the dhcp_release process crashes with a core dump, disrupting DHCP lease release functionality on the affected host. There is no impact on confidentiality or integrity — only availability is affected. The scope is limited to the local system running dnsmasq-utils 2.79-1, with no known potential for lateral movement or data exfiltration (Red Hat Advisory, Red Hat Bugzilla).

A proof-of-concept exploit is publicly available on Exploit-DB (EDB-48301), though there is no evidence of active in-the-wild exploitation at this time (VulnCheck Advisory). The EPSS score is approximately 0.017% (0.000170), indicating a very low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, and no threat actor attribution has been reported (Red Hat Advisory).

1. Identify target: Confirm the target system is running dnsmasq-utils version 2.79-1 on a Linux host (e.g., Ubuntu with the package from launchpad.net/ubuntu/+source/dnsmasq/2.79-1).
2. Access the system: Obtain local access to the system (e.g., via an existing shell session or local user account), as the attack vector is local.
3. Craft oversized input: Prepare an input string exceeding 16 characters to be passed as an argument to the dhcp_release utility.
4. Execute the exploit: Run dhcp_release with the crafted oversized string as input (e.g., dhcp_release <interface> <ip> <mac> <AAAAAAAAAAAAAAAAA...> where the relevant argument exceeds 16 characters).
5. Observe crash: The dhcp_release process overflows its stack buffer, generates a core dump, and terminates — achieving denial of service of the DHCP release functionality (Exploit-DB, VulnCheck Advisory).

• Logs: Unexpected core dump entries in system logs (e.g., /var/log/syslog or journalctl) referencing dhcp_release process crashes; kernel messages such as dhcp_release[PID]: segfault at ....
• File System: Presence of core dump files (e.g., core, core.<pid>) in the working directory or configured core dump path following dhcp_release execution.
• Process: Abnormal termination of the dhcp_release process with a non-zero exit code or signal (SIGSEGV/SIGABRT) visible in process accounting logs.

Upgrade dnsmasq-utils to a version beyond 2.79-1 that includes the fix for this buffer overflow. Red Hat has tracked the patch via Bugzilla bug 2437103; users should apply vendor-provided updates as they become available for their distribution (Red Hat Bugzilla). As a workaround, restrict local access to the dhcp_release binary using file permissions or access controls, and monitor for unexpected crashes or core dumps of the process. Network-level controls limiting who can invoke DHCP release functionality can also reduce exposure (Red Hat Advisory).