Summary
Hickory DNS's Record Cache Accepts AUTHORITY-Section NS from Sibling Zone via Parent-Pool Zone-Context Elevation
The Hickory DNS project's experimental hickory-recursor crate's record cache (DnsLru) stores records from DNS responses keyed by each record's own (name, type), not by the query that triggered the response. cache_response() in crates/recursor/src/lib.rs chains ANSWER, AUTHORITY, and ADDITIONAL sections into one record iterator before insertion. The bailiwick filter it applies uses the zone context of the NS pool that serviced the lookup, not the zone being queried.
This creates a cross-zone poisoning path. When Hickory builds the NS pool for attacker.poc. it uses the parent poc. NS pool (ns.zone() = "poc."). If the poc. nameserver under the attacker's control includes in its response's AUTHORITY section a record for a sibling zone like victim.poc. NS ns.evil.poc., the bailiwick check is_subzone("poc.", "victim.poc.") passes (victim.poc. is a subdomain of poc.). The record is stored under (victim.poc., NS) in the shared cache.
Subsequently, any client querying a name in victim.poc. causes Hickory to build its NS pool from the poisoned cache entry, routing queries to the attacker's nameserver (ns.evil.poc.) rather than to the legitimate nameserver for victim.poc.. The legitimate NS for that zone receives zero queries.
This issue is fixed in hickory-resolver 0.26.0 with the recursor feature through an architectural change to response-level caching: responses are stored keyed by the originating query (name, type). A response to (attacker.poc. NS) is stored only under that key and cannot affect the (victim.poc., NS) cache entry.
Hickory DNS believes this issue has been present in all published versions of the experimental hickory-recursor crate, which has now been folded into the hickory-resolver crate under the non-default recursor feature flag. The hickory-recursor crate will not receive any updates going forward and all users should migrate to hickory-resolver with the recursor feature.
Users of the hickory-dns binary configured with the opt-in recursor feature and a configuration acting as a recursive resolver should update to 0.26.0+.
Reporter
Qifan Zhang, Palo Alto Networks
Impact
Affected versions
Security releases
Kodem intelligence
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Frequently Asked Questions
- What is GHSA-83HF-93M4-RGWQ? GHSA-83HF-93M4-RGWQ is a high-severity security vulnerability in hickory-recursor (rust), affecting versions >= 0.24.0, <= 0.25.2. It is fixed in 0.26.0.
- Which versions of hickory-recursor are affected by GHSA-83HF-93M4-RGWQ? hickory-recursor (rust) versions >= 0.24.0, <= 0.25.2 is affected.
- Is there a fix for GHSA-83HF-93M4-RGWQ? Yes. GHSA-83HF-93M4-RGWQ is fixed in 0.26.0. Upgrade to this version or later.
- Is GHSA-83HF-93M4-RGWQ exploitable, and should I be worried? Whether GHSA-83HF-93M4-RGWQ is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-83HF-93M4-RGWQ is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-83HF-93M4-RGWQ? Upgrade
hickory-recursorto 0.26.0 or later.