{"id":"CVE-2026-16729","aliases":["GHSA-v3r7-h72x-cjcm"],"title":"undici vulnerable to cookie attribute injection via unsanitized domain and unparsed setCookie fields","summary":"undici vulnerable to cookie attribute injection via unsanitized domain and unparsed setCookie fields","severity":"medium","cvss":4.8,"cwe":["CWE-74"],"vendor":"undici","product":"undici","ecosystem":"npm","affected":["undici < 6.28.0","undici >= 7.0.0, < 7.29.0","undici >= 8.0.0, < 8.9.0"],"patched":["undici 6.28.0","undici 7.29.0","undici 8.9.0"],"published":"2026-08-03","updated":"2026-08-03","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-v3r7-h72x-cjcm","references":[{"url":"https://github.com/nodejs/undici/security/advisories/GHSA-v3r7-h72x-cjcm"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-16729"},{"url":"https://github.com/nodejs/undici/commit/10d93fc332f2c8c161982dec3833201de29891b5"},{"url":"https://github.com/nodejs/undici/commit/3bf91ddb493e853957f3a58e155326a668ab8aef"},{"url":"https://github.com/nodejs/undici/commit/af7484043ee075a6f216da0ad77e1dac55199235"},{"url":"https://cna.openjsf.org/security-advisories.html"},{"url":"https://github.com/nodejs/undici/releases/tag/v6.28.0"},{"url":"https://github.com/nodejs/undici/releases/tag/v7.29.0"},{"url":"https://github.com/nodejs/undici/releases/tag/v8.9.0"},{"url":"https://github.com/advisories/GHSA-v3r7-h72x-cjcm"}],"tags":["ghsa","npm"],"epss":0.00191,"epssPercentile":0.08992,"ingestedAt":"2026-08-03T20:29:32.731Z","slug":"CVE-2026-16729","body":"## Overview\n\n## Impact\n\nThe `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`.\n\nApplications 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.\n\n## Patches\n\nPatched in undici v6.28.0, v7.29.0, and v8.9.0.\n\n## Workarounds\n\n- Sanitize `domain` values against the RFC 1034 letter-digit-hyphen set before passing to `setCookie`.\n- Do not pass user-controlled data to the `unparsed` field.\n\n## Affected packages\n\n- `undici < 6.28.0`\n- `undici >= 7.0.0, < 7.29.0`\n- `undici >= 8.0.0, < 8.9.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `undici 6.28.0`\n- `undici 7.29.0`\n- `undici 8.9.0`","depth":"sunlit","depthScore":26,"depthScoreParts":{"impact":26.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}