CVE-2026-14643
MEDIUMCVE-2026-14643 is a medium-severity (CVSS 5.9) CWE-436 vulnerability in undici. O3 Security confirms whether CVE-2026-14643 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
undici vulnerable to cross-user information disclosure via whitespace around equals in Cache-Control directives
Blast Radius
undici📦undiciReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
undici's cache interceptor mishandles optional whitespace placed around the equals sign of a qualified no-cache or private Cache-Control directive. In undici from 7.0.0 up to before 7.29.0 and from 8.0.0 up to before 8.9.0, the parser either drops the directive or stores a field name with literal quote characters, so the cache decision fails to recognize the qualification and the response is stored. In shared-cache mode, this lets a response containing one user's authenticated data be served from cache to a later caller, including an unauthenticated one, when both requests resolve to the same cache key. It affects applications that enable the cache interceptor in shared mode, forward Authorization headers upstream, and receive cacheable responses with qualified directives padded with whitespace around the equals sign. This is the whitespace-around-equals variant that the fix for CVE-2026-9678 did not normalize, and it is fixed in undici 7.29.0 and 8.9.0.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | undici | ≥ 7.0.0&&< 7.29.0 | 7.29.0 |
| 📦npm | undici | ≥ 8.0.0&&< 8.9.0 | 8.9.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for undici. 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 undici to 7.29.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-14643 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-2026-14643 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-2026-14643. 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-2026-14643 in your dependencies?
O3 detects CVE-2026-14643 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.