CVE-2026-24401: Avahi has Uncontrolled Recursion in lookup_handle_cname function
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 lookuphandlecname function, leading to stack exhaustion. The vulnerability affects record browsers where AVAHILOOKUPUSEMULTICAST is set explicitly, which includes record browsers created by resolvers used by nss-mdns. This issue is patched in commit 78eab31128479f06e30beb8c1cbf99dd921e2524, which is part of version 0.9-rc3.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
debian/avahito a version that resolves this vulnerability.Fixed in 0.8-18 - Upgrade
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ubuntu/avahito a version that resolves this vulnerability.Fixed in 0.6.31-4ubuntu1.3+esm5 - Upgrade
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ubuntu/avahito a version that resolves this vulnerability.Fixed in 0.6.32~rc+dfsg-1ubuntu2.3+esm5 - Upgrade
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ubuntu/avahito a version that resolves this vulnerability.Fixed in 0.7-3.1ubuntu1.3+esm4 - Upgrade
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ubuntu/avahito a version that resolves this vulnerability.Fixed in 0.7-4ubuntu7.3+esm2 - Upgrade
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ubuntu/avahito a version that resolves this vulnerability.Fixed in 0.8-5ubuntu5.5 - Upgrade
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ubuntu/avahito a version that resolves this vulnerability.Fixed in 0.8-13ubuntu6.2 - Upgrade
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ubuntu/avahito a version that resolves this vulnerability.Fixed in 0.8-16ubuntu3.2 - Upgrade
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Avahito a version that resolves this vulnerability.Fixed in 0.9-rc3Patch 78eab31128479f06e30beb8c1cbf99dd921e2524
Event History
Frequently Asked Questions
What is the severity of CVE-2026-24401?
CVE-2026-24401 has been classified as a high severity vulnerability due to its potential to crash the avahi-daemon.
How do I fix CVE-2026-24401?
To mitigate CVE-2026-24401, upgrade to a version of Avahi beyond 0.9rc2.
What causes the CVE-2026-24401 vulnerability?
CVE-2026-24401 is caused by uncontrolled recursion in the lookup_handle_cname function of the avahi-daemon.
Which versions of Avahi are affected by CVE-2026-24401?
Avahi versions 0.9rc2 and below are affected by CVE-2026-24401.
What impact does CVE-2026-24401 have on systems running Avahi?
CVE-2026-24401 can lead to a segmentation fault, causing the avahi-daemon to crash.