CVE-2026-42254
MEDIUMCVE-2026-42254 is a medium-severity (CVSS 4) CWE-706 vulnerability in hickory-recursor. O3 Security confirms whether CVE-2026-42254 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Hickory DNS's Record Cache Accepts AUTHORITY-Section NS from Sibling Zone via Parent-Pool Zone-Context Elevation
Blast Radius
hickory-recursor🦀hickory-recursorReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Hickory DNS hickory-recursor 0.1 through 0.25.2 allows cross-zone poisoning because cached data is not directly associated with a query that triggered a response.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | hickory-recursor | ≥ 0.24.0&&< 0.26.0 | 0.26.0 |
| 🦀crates.io | hickory-recursor | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hickory-recursor. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update hickory-recursor to 0.26.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42254 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-42254 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-42254. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-42254 in your dependencies?
O3 detects CVE-2026-42254 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.