Bug 2432534 (CVE-2026-24401)

Summary: CVE-2026-24401 avahi: Avahi: Denial of Service via recursive CNAME record in mDNS response
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Avahi, a system that enables devices to discover services on a local network. A remote attacker can exploit this vulnerability by sending a specially crafted mDNS (multicast Domain Name System) response containing a recursive CNAME (Canonical Name) record. This triggers an uncontrolled recursion within the avahi-daemon process, leading to stack exhaustion and causing the service to crash. This results in a denial of service (DoS) for affected systems.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2433674, 2433675    
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Description OSIDB Bzimport 2026-01-24 02:02:02 UTC 
Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In versions 0.9rc2 and below, avahi-daemon can be crashed via a segmentation fault by sending an unsolicited mDNS response containing a recursive CNAME record, where the alias and canonical name point to the same domain (e.g., "h.local" as a CNAME for "h.local"). This causes unbounded recursion in the lookup_handle_cname function, leading to stack exhaustion. The vulnerability affects record browsers where AVAHI_LOOKUP_USE_MULTICAST is set explicitly, which includes record browsers created by resolvers used by nss-mdns. This issue is patched in commit 78eab31128479f06e30beb8c1cbf99dd921e2524.