Critical Vulnerabilities in dnsmasq Expose Systems to DoS and Code Execution Risks

Severity: High (Score: 74.0)

Sources: Kb.Cert, Linuxsecurity

Summary

Multiple vulnerabilities have been identified in dnsmasq, an open-source DNS and DHCP server, affecting various Linux distributions, including Ubuntu. The vulnerabilities, tracked as CVE-2026-2291, CVE-2026-4890, CVE-2026-4891, CVE-2026-4892, CVE-2026-4893, and CVE-2026-5172, allow attackers to exploit memory safety issues, leading to potential Denial of Service (DoS) and local privilege escalation. Specifically, CVE-2026-2291 allows for DNS cache poisoning, while CVE-2026-4890 can cause infinite loops, resulting in service outages. The vulnerabilities were published on May 11, 2026, and patches have been released for affected systems. Users are urged to update their dnsmasq installations to mitigate these risks. The vulnerabilities primarily affect Ubuntu versions 16.04 LTS through 26.04 LTS. Key Points: • dnsmasq has multiple critical vulnerabilities allowing DoS and code execution. • Affected systems include various versions of Ubuntu from 16.04 to 26.04 LTS. • Patches are available; users must update to secure their systems.

Key Entities

• Data Breach (attack_type)
• DDoS (attack_type)
• CVE-2026-2291 (cve)
• CVE-2026-4890 (cve)
• CVE-2026-4891 (cve)
• CVE-2026-4892 (cve)
• CVE-2026-4893 (cve)
• Cwe-122 - Heap-based Buffer Overflow (cwe)
• Cwe-125 - Out-of-bounds Read (cwe)
• CWE-200 - Exposure of Sensitive Information (cwe)
• CWE-269 - Improper Privilege Management (cwe)
• Cwe-787 - Out-of-bounds Write (cwe)
• gmail.com (domain)
• xchglabs.com (domain)
• T1068 - Exploitation for Privilege Escalation (mitre_attack)
• DNSmasq (tool)
• Ubuntu (company)