Hickory DNS 0.25.0-alpha.3 through 0.25.2 Query Amplification via Cyclic Referrals
cve-program · CVE-2026-123586
PublishedHickory 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.
Read the publisher's advisoryeuvd · EUVD-2026-119345
PublishedHickory 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.
Read the publisher's advisorynvd · CVE-2026-123586
PublishedHickory 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.
Read the publisher's advisoryosv · RUSTSEC-2026-0516
PublishedTwo 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.
Read the publisher's advisoryosv · RUSTSEC-2026-0522
PublishedTwo 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.
Read the publisher's advisoryAffected versions, risk and source history
Exploitation and risk
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cve-program · CVE-2026-123586
PublishedHickory DNS 0.25.0-alpha.3 through 0.25.2 Query Amplification via Cyclic Referrals
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.
- Source published
- 8 Nov 2026 01:38:18 UTC
- Source modified
- 9 Nov 2026 13:54:36 UTC
- Saved here
- 9 Nov 2026 15:02:10 UTC
- Source terms
- CVE Program Terms of Use
Original source record · Cite this exact observation · Complete original publisher JSON
Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
euvd · EUVD-2026-119345
PublishedHickory 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 serve…
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.
Additional publisher context
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
- Source published
- Nov 8, 2026, 1:38:18 AM (timezone not stated)
- Source modified
- Nov 9, 2026, 1:54:36 PM (timezone not stated)
- Saved here
- 12 Nov 2026 15:19:05 UTC
- Source terms
- ENISA EUVD · source terms and attribution apply
Original source record · Cite this exact observation · Complete original publisher JSON
Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
EUVD CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
nvd · CVE-2026-123586
PublishedHickory 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 serve…
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.
Additional publisher context
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
- Source published
- 8 Nov 2026 02:16:52 UTC
- Source modified
- 10 Nov 2026 22:15:59 UTC
- Saved here
- 12 Nov 2026 15:18:38 UTC
- Source terms
- NIST NVD usage terms; underlying source attribution retained
Original source record · Cite this exact observation · Complete original publisher JSON
Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 4.0 · [email protected] · Secondary · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
osv · RUSTSEC-2026-0516
PublishedRecursor kept querying cyclic glueless sibling delegations
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.
- Source published
- 3 Sep 2026 12:00:00 UTC
- Source modified
- 12 Nov 2026 14:40:46 UTC
- Saved here
- 12 Nov 2026 15:18:33 UTC
- Source terms
- OSV · upstream source license applies
Original source record · Cite this exact observation · Complete original publisher JSON
Source: osv · OSV · upstream source license applies. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
osv · RUSTSEC-2026-0522
PublishedRecursor kept querying cyclic glueless sibling delegations (no fixed hickory-recursor release)
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.
- Source published
- 3 Sep 2026 12:00:00 UTC
- Source modified
- 12 Nov 2026 14:40:46 UTC
- Saved here
- 12 Nov 2026 15:18:33 UTC
- Source terms
- OSV · upstream source license applies
Original source record · Cite this exact observation · Complete original publisher JSON
Source: osv · OSV · upstream source license applies. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.