undici vulnerable to cross-user information disclosure via shared cache whitespace bypass
- When
- Where
- Global (internet)
- Category
- cyber_advisory · npm
## Impact Undici's cache interceptor incorrectly classifies some responses as cacheable when the upstream `Cache-Control` header uses whitespace-padded qualified `private` or `no-cache` field names such as `private=" authorization"` or `no-cache="\tauthorization"`. The parser preserves the surrounding whitespace, so later comparisons against the literal `authorization` field name fail and the response is stored. In shared-cache mode, this allows a response containing one user's authenticated data to be served from cache to a subsequent caller, including an unauthenticated caller, when both requests resolve to the same cache key. Affected applications are those that explicitly enable the cache interceptor (`interceptors.cache()`) in shared mode, forward `Authorization` headers upstream, and receive cacheable responses with non-canonical qualified `private` or `no-cache` directives. ## Patches Upgrade to undici v7.28.0 or v8.5.0. ## Workarounds If upgrade is not immediately possible, disable shared-cache mode for traffic that includes `Authorization` headers, avoid caching responses to authenticated requests, or add `Vary: Authorization` upstream.
Sources
- GitHub Advisory Database ↗ · first seen 2026-06-18 14:28 UTC
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