CVE-2026-84961High· 7.4▾ Twilightundici's BalancedPool constructor passes its entire options object through an internal deep-clone that serializes and reparses the value as JSON. Because JSON cannot represent functions, any function-valued TLS option, such as a caller-s…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 40.7 · likelihood 0 · exploitation 0
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Exploit-prediction probability, daily snapshots since Sep 8.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
0.1%
Last analysed / modified upstream
0.1% → 0.1%
undici's BalancedPool constructor passes its entire options object through an internal deep-clone that serializes and reparses the value as JSON. Because JSON cannot represent functions, any function-valued TLS option, such as a caller-supplied checkServerIdentity callback or a custom connector inside the connect option, is silently discarded before it reaches the TLS layer. As a result a peer whose certificate the application's custom checkServerIdentity was written to reject, but which still passes Node's default hostname and chain checks, is accepted when reached through BalancedPool. The Client, Pool, and Agent dispatchers are not affected because they extract the connect and tls options before cloning. This affects undici versions from 7.24.1 up to 7.29.1 and from 8.0.0 up to 8.10.2, and only when the application supplies a function-valued connect or tls option to BalancedPool. Users should upgrade to undici 7.29.1 or 8.10.2.
undici >= 7.24.1, < 7.29.1undici >= 8.0.0, < 8.10.2Upgrade past the affected range:
undici 8.10.2Connected by shared product, vendor, weakness, or advisory.
CVE-2026-84890Medium· 5.9undici's decompress interceptor decompresses response bodies according to the untrusted Content-Encoding header
CVE-2026-18149Medium· 5.9undici's retry handler can leave an already-exposed response body pending forever
CVE-2026-18540Low· 3.7undici's retry interceptor can append the body of a ranged retry response to bytes already delivered from an earlier partial response while still presenting the original response's status and headers
CVE-2026-19534High· 7.5undici's WebSocket client crashes the whole Node.js process during the opening handshake when a server responds with a subprotocol that the client never requested
CVE-2026-84933Medium· 6.5undici's cache interceptor does not handle the Set-Cookie response header anywhere in its cache path, so it neither refuses to store nor strips that header
CVE-2026-84947Low· 3.7undici's dump interceptor reads and discards a response body up to a configurable maximum size