CVE-2026-9678 undici vulnerable to cross-user information disclosure via shared cache whitespace bypass
Attackers can read other users' authenticated data via shared cache when whitespace-padded cache headers bypass security checks in undici.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-9678?
CVE-2026-9678 is a medium-severity vulnerability in Nodejs Undici, published on 17 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-524
Which versions are affected by CVE-2026-9678?
4 open source packages ship an affected version, including undici. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
undici npm | From 7.0.0 | 7.28.0 |
undici npm | From 7.0.0 | 7.28.0 |
undici npm | From 8.0.0 | 8.5.0 |
undici npm | From 8.0.0 | 8.5.0 |
Products include Nodejs Undici.
How do I fix CVE-2026-9678?
Upgrade undici to a fixed version for your release line: 7.28.0 or 8.5.0.
Is CVE-2026-9678 being exploited?
There is no known exploitation of CVE-2026-9678 in the wild and no public exploit code.
Other vulnerabilities in Nodejs Undici
- CVE-2026-109855 undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake
- CVE-2026-109869 undici vulnerable to Denial of Service via unhandled error on excessive content-encodings
- CVE-2026-87018 undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation
- CVE-2026-19534 undici vulnerable to Denial of Service via unrequested WebSocket subprotocol
- CVE-2026-12151 undici WebSocket client vulnerable to denial of service via fragment count bypass
Sources
Also known as DEBIAN-CVE-2026-9678, ECHO-8994-d1aa-91ab, GHSA-pr7r-676h-xcf6, MINI-37m7-pqxf-864q, MINI-49jg-32vr-h3xx, MINI-4qj9-vj73-vfwv and 8 more.