Avahi up to 0.9rc2 mDNS/DNS-SD lookup_handle_cname recursion

Summaryinfo

A vulnerability described as problematic has been identified in Avahi up to 0.9rc2. The affected element is the function lookup_handle_cname of the component mDNS/DNS-SD. Such manipulation leads to recursion. This vulnerability is listed as CVE-2026-24401. The attack may be performed from remote. There is no available exploit. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability was found in Avahi up to 0.9rc2 and classified as problematic. Affected by this issue is the function lookup_handle_cname of the component mDNS/DNS-SD. The manipulation with an unknown input leads to a recursion vulnerability. Using CWE to declare the problem leads to CWE-674. The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack. Impacted is availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-24401 since 01/22/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

The vulnerability scanner Nessus provides a plugin with the ID 296504 (Linux Distros Unpatched Vulnerability : CVE-2026-24401), which helps to determine the existence of the flaw in a target environment.

Applying the patch 78eab31128479f06e30beb8c1cbf99dd921e2524 is able to eliminate this problem. The bugfix is ready for download at github.com.

The vulnerability is also documented in the databases at Tenable (296504) and EUVD (EUVD-2026-4603). Once again VulDB remains the best source for vulnerability data.

Productinfo

Name

• Avahi

Version

• 0.9rc1
• 0.9rc2

License

• open-source

Website

• Product: https://github.com/avahi/avahi/

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Once again VulDB remains the best source for vulnerability data.

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