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CVE-2026-55717 is a denial-of-service vulnerability in NLnet Labs Unbound affecting versions 1.10.0 through 1.25.1. The flaw is triggered when Unbound is configured with serve-expired: yes together with a response-ip redirect rule that rewrites matching addresses to a CNAME target, or the equivalent RPZ CNAME override behavior. In the serve-expired-client-timeout callback, Unbound performs a two-pass loop to chase the CNAME alias generated by the response-ip logic. On the second pass, the code resets alias_rrset but does not reset partial_rep, leaving internal state inconsistent. That inconsistency later causes a NULL pointer dereference and crashes the daemon.
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serve-expired: yes together with response-ip redirect plus CNAME rewrite rules, or the equivalent RPZ rpz-cname-override behavior. Review and restrict response-ip or RPZ policies that can be matched by attacker-controlled A or AAAA answers, and disable serve-expired or the redirect/CNAME rewrite feature where operationally feasible.Patch, then assume compromise.
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No public exploit code observed for this vulnerability.
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3 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.
No news coverage yet. Advisories and community discussion only.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.