GHSA-6w6g-hm98-mhgm
hickory-resolver: Unbounded TC-retry loop in `NameServerPool::try_send` (resource-exhaustion DoS)
- Risk score
- 57/100
- CVSS
- 8.7 v4.0
- Published
- 5 Oct 2026
Open in the live forecast Today's forecast
What to know
- What it is
- When the hickory-resolver name server pool implementation receives an upstream response with the TC (truncated) header bit set, it re-queues the request to the same nameserver to retry with UDP transport disabled. However, the retry arm never inspects the transport that just answered and carries no iteration counter. …
- Affected
- hickory-resolver (rust) >= 0.26.0-beta.1, < 0.26.2
- Fix
- Upgrade hickory-resolver to 0.26.2 or later.
- Exploitation
- No known exploitation
Why it is Yellow
- CVSS 8.7 high
- Remotely exploitable without logging in
Affected packages
| Package | Ecosystem | Vulnerable | Fixed in |
|---|---|---|---|
| hickory-resolver | rust | >= 0.26.0-beta.1, < 0.26.2 | 0.26.2 |
References
- https://github.com/advisories/GHSA-6w6g-hm98-mhgm
- https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-6w6g-hm98-mhgm
- https://github.com/hickory-dns/hickory-dns/pull/3871
- https://github.com/hickory-dns/hickory-dns/commit/0848d2e9e4183499343318a690d6dd5e48bc21c1
- https://github.com/hickory-dns/hickory-dns/commit/5d37e2e04a36a87013a213b58b820345ef76a263
- https://github.com/hickory-dns/hickory-dns/releases/tag/v0.26.2
- https://github.com/advisories/GHSA-6w6g-hm98-mhgm
Original description
When the `hickory-resolver` name server pool implementation receives an upstream response with the TC (truncated) header bit set, it re-queues the request to the same nameserver to retry with UDP transport disabled. However, the retry arm never inspects the transport that just answered and carries no iteration counter. An authoritative server that sets `TC=1` on **every** available transport keeps the resolver spinning on one persistent TCP connection until the 5s per-request wall-clock deadline expires. ### Reporter Qifan Zhang, Palo Alto Networks
Last activity 5 Oct 2026. Patch Forecast updates every hour.