CVE-2026-14643: undici vulnerable to cross-user information disclosure via whitespace around equals in Cache-Control directives

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-29 · updated 2026-08-04
Weakness: CWE-436

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 products

undici: from 7.0.0 before 7.29.0; from 8.0.0 before 8.9.0 — fixed in 7.29.0, 8.9.0

How to fix

Upgrade to a fixed version: undici 7.29.0, 8.9.0. Check the vendor advisory for mitigations.

References

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