Hickory DNS 0.25.0-alpha.3 through 0.25.2 contains a query amplification vulnerability in its recursive resolver, which mishandles cyclic sibling name server referrals that lack glue records. Attackers controlling two zones whose name servers reference each other without glue records can make the recursor loop, sending many upstream queries, amplified further by zero-TTL NS records.
Hickory DNS 0.25.0-alpha.3 through 0.25.2 contains a query amplification vulnerability in its recursive resolver, which mishandles cyclic sibling name server referrals that lack glue records. Attackers controlling two zones whose name servers reference each other without glue records can make the recursor loop, sending many upstream queries, amplified further by zero-TTL NS records.
Hickory DNS 0.25.0-alpha.3 through 0.25.2 contains a query amplification vulnerability in its recursive resolver, which mishandles cyclic sibling name server referrals that lack glue records. Attackers controlling two zones whose name servers reference each other without glue records can make the recursor loop, sending many upstream queries, amplified further by zero-TTL NS records.
Two zones can each delegate to name servers named only inside the other zone, with no glue records (the cyclic sibling case in RFC 9471 section 2.3). Such delegations can never be resolved, but the recursor did not stop when it came back to a zone it was already resolving. It kept sending queries until the per-request limits ran out, and zero TTLs on the referral NS records made this worse.
Someone who controls two such zones can make a recursor send many upstream queries for each client query.
This affects the recursive resolver, which is in hickory-resolver behind the opt-in `recursor` feature from 0.26.0-beta.1. Earlier releases shipped it as the separate hickory-recursor crate.
From 0.26.2 each client request tracks the zones on its resolution stack and refuses to enter a zone that is already on it.
Two zones can each delegate to name servers named only inside the other zone, with no glue records (RFC 9471 section 2.3). The recursor did not stop when it came back to a zone it was already resolving, so someone who controls two such zones can make it send many upstream queries for each client query.
The recursor code moved into hickory-resolver (opt-in `recursor` feature) in 0.26.0-beta.1, and the fix is in hickory-resolver 0.26.2. No hickory-recursor release contains a fix, so users should move to hickory-resolver 0.26.2 or later with the `recursor` feature.
EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.
Original publisher date fields
datePublished: Nov 8, 2026, 1:38:18 AM
dateUpdated: Nov 9, 2026, 1:54:36 PM
No normalized affected-package data is projected for this source revision. The original publisher record may contain additional product and version evidence; this does not establish that a package is unaffected.
NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.
Source analysis status: Deferred
Weakness classifications: CWE-400
Original publisher date fields
published: 2026-11-08T02:16:52.477
lastModified: 2026-11-10T22:15:59.797
No normalized affected-package data is projected for this source revision. The original publisher record may contain additional product and version evidence; this does not establish that a package is unaffected.