undici vulnerable to cookie attribute injection via unsanitized domain and unparsed setCookie fields
## Impact The `setCookie` function has two attribute injection paths. `validateCookieDomain` does not reject semicolons (`validateCookiePath` already does at 0x3B), so a `domain` value like `example.com; SameSite=None` lands verbatim as `Domain=example.com; SameSite=None`. The `unparsed` array's loop only checks each entry contains `=` and does not sanitize values, so an entry like `X-Custom=val; HttpOnly` lands unchanged, injecting `HttpOnly` without the caller setting `cookie.httpOnly = true`. Applications that pass user-controlled input to these fields, typically multi-tenant or reverse-proxy servers that scope session cookies to a tenant-supplied domain, can have SameSite CSRF protections bypassed, `Secure` or `HttpOnly` forced or stripped, or the intended SameSite tier overridden. ## Patches Patched in undici v6.28.0, v7.29.0, and v8.9.0. ## Workarounds - Sanitize `domain` values against the RFC 1034 letter-digit-hyphen set before passing to `setCookie`. - Do not pass user-controlled data to the `unparsed` field.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-16729US | medium6.5 | — | ||
undici's setCookie function does not fully sanitize cookie attributes. In undici before 6.28.0, from 7.0.0 up to before 7.29.0, and from 8.0.0 up to before 8.9.0, a domain value is… | ||||
references
External citations — patches, advisories, analysis.
- https://cna.openjsf.org/security-advisories.htmlWEB
- https://github.com/nodejs/undiciPACKAGE
- https://github.com/nodejs/undici/commit/10d93fc332f2c8c161982dec3833201de29891b5WEB
- https://github.com/nodejs/undici/commit/3bf91ddb493e853957f3a58e155326a668ab8aefWEB
- https://github.com/nodejs/undici/commit/af7484043ee075a6f216da0ad77e1dac55199235WEB
- https://github.com/nodejs/undici/releases/tag/v6.28.0WEB
- https://github.com/nodejs/undici/releases/tag/v7.29.0WEB
- https://github.com/nodejs/undici/releases/tag/v8.9.0WEB
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