In NLnet Labs Unbound 1.18.0 up to and including 1.25.1, when Unbound listens on a proxy-protocol-port interface with answer-cookie: yes, the RFC 9018 server-cookie SipHash is computed over the proxys wire address instead of the PROXYv2-declared client. One server cookie obtained through a given proxy node therefore validates for every PROXYv2-declared source behind that node. On a UDP+proxy-protocol front, an off-path attacker can harvest one cookie with a single legitimate query, then replay it under any spoofed source and pass DNS Cookie checks that were deployed to defeat this in the first place.
Weakness
This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Unbound | Nlnetlabs | 1.18.0 (including) | 1.25.2 (excluding) |
| Red Hat Hardened Images | RedHat | unbound-main-1.25.2-0.1.hum1 | * |
| Unbound | Ubuntu | upstream | * |
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/21.html
- https://cwe.mitre.org/data/definitions/22.html
- https://cwe.mitre.org/data/definitions/459.html
- https://cwe.mitre.org/data/definitions/461.html
- https://cwe.mitre.org/data/definitions/473.html
- https://cwe.mitre.org/data/definitions/476.html
- https://cwe.mitre.org/data/definitions/59.html
- https://cwe.mitre.org/data/definitions/60.html
- https://cwe.mitre.org/data/definitions/667.html
- https://cwe.mitre.org/data/definitions/94.html