CVE-2026-123591

Hickory DNS hickory-resolver 0.26.0-beta.1 before 0.26.2 contains an unbounded retry loop in NameServerPool::try_send that re-queues truncated (TC) responses without checking the answering transport or counting iterations. A malicious authoritative server returning TC=1 on every transport keeps the resolver spinning on a persistent TCP connection until the 5-second request deadline expires, causing resource exhaustion.

hickory-proto and hickory-resolver 0.26.0 before 0.26.2, hickory-server 0.25.0-alpha.1 before 0.26.2, and hickory-recursor 0.25.0-alpha.3 through 0.26.0-alpha.1 fail to canonicalize IPv4-mapped IPv6 addresses when checking deny_answers, deny_server, or AccessControlSet rules. Attackers can use IPv4-mapped addresses to evade answer filtering, trigger queries to denied nameservers, or reach hickory-server library deployments on dual-stack IPv6 sockets from denied clients.

The Hickory DNS recursor in all versions of hickory-recursor and in hickory-resolver 0.26.0-beta.1 before 0.26.2 (recursor feature) is vulnerable to ghost domain names attacks because it reuses child-side apex NS RRsets cached from zone NS queries for iterative resolution. By repeatedly querying a zone's NS records, an attacker keeps the stale RRset cached indefinitely, letting name servers whose delegation the parent revoked keep answering for the zone.

Hickory DNS hickory-proto 0.25.0 through 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2 invert the relational operators in the wrap-around branch of find_covering_record() in nsec3.rs, so the last NSEC3 record in a zone's hash ring covers every hash except its owner. Attackers able to inject DNS responses can replay that NSEC3 record and its RRSIG to forge DNSSEC-validated negative responses denying legitimate names.

Hickory DNS hickory-proto 0.25.0-alpha.3 through 0.25.2 and hickory-net 0.26.0-alpha.1 before 0.26.2 contain a DNSSEC validation flaw in DnssecDnsHandle that accepts NSEC3-signed NODATA responses for zone-apex queries as secure without an NSEC3 record matching the hashed QNAME. On-path attackers or malicious authoritative servers can replay a validly signed non-apex NSEC3 with the zone's signed SOA to serve an authenticated (AD=1) denial of any apex RRtype for the negative-cache TTL.

Hickory DNS hickory-proto before 0.26.0-beta.1 and hickory-net before 0.26.2 contain a DNSSEC validation bypass because verify_rrsets() ignores DNS class when partitioning RRsets, so non-IN records skip signature verification yet are marked secure when the IN records verify. Attackers able to supply DNS responses can include forged CH or HS class records, including DS records, to authenticate any DNSKEY and forge child zone responses.

The validating recursor in Hickory DNS hickory-recursor 0.25.0 through 0.26.0-alpha.1, hickory-resolver 0.26.0-alpha.1 before 0.26.2, and hickory-net 0.26.0-beta.1 before 0.26.2 caches DNSSEC-bogus answers using the untrusted, attacker-supplied record TTL (capped at 24 hours) instead of a short validation-failure TTL. A remote attacker who spoofs a single authoritative response with an invalid signature and a long TTL can keep the bogus result cached for up to 24 hours.

Hickory DNS hickory-proto 0.25.0-alpha.1 through 0.26.0-alpha.1 and hickory-net before 0.26.2 contain a logic bug in DnssecDnsHandle's DS-fetch path that caches transient DS lookup errors as Bogus DNSSEC validation verdicts. An attacker who induces a SERVFAIL, REFUSED, or timeout response to a child-zone DS sub-query causes the validator to return SERVFAIL for all names under that zone until the cache entry's TTL expires.

Hickory DNS hickory-proto through 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2 contain a DNSSEC validation flaw in the validating recursor's NSEC handler that accepts parent-side ancestor-delegation NSEC records as proof of nonexistence for names below the zone cut. An on-path attacker, rogue parent nameserver, or attacker winning a port and TXID race can deliver one forged NXDOMAIN response built from genuinely signed parent NSEC records, causing authenticated denial of existing child-zone names cached for the negative TTL.

Hickory DNS hickory-proto 0.25 through 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2 contain a DNSSEC validation flaw in the validating recursor's NSEC3 handler, which matches the closest encloser by hash alone without checking the type bitmap and so accepts parent-side ancestor-delegation NSEC3 records as proof of nonexistence. An attacker who delivers one response built from genuinely signed parent NSEC3 records can cause NXDOMAIN or NODATA to be cached with AD=1, denying resolution of existing names at and below the zone cut.