Improper Neutralization Affecting undici package, versions <6.28.0>=7.0.0 <7.29.0>=8.0.0 <8.9.0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-UNDICI-18426061
- published30 Jul 2026
- disclosed29 Jul 2026
- creditZelys-DFKH
Introduced: 29 Jul 2026
NewCVE-2026-16729 (opens in a new tab)How to fix?
Upgrade undici to version 6.28.0, 7.29.0, 8.9.0 or higher.
Overview
undici is an An HTTP/1.1 client, written from scratch for Node.js
Affected versions of this package are vulnerable to Improper Neutralization via unsanitized domain handling and unparsed attribute serialization in lib/web/cookies/util.js. An attacker can inject or override cookie attributes by supplying a crafted domain such as example.com; SameSite=None or an unparsed entry such as X-Custom=val; HttpOnly to setCookie. When applications pass user-controlled tenant or routing data into these fields, the serialized Set-Cookie header can carry attacker-chosen flags like SameSite, Secure, or HttpOnly. This can weaken CSRF protections, alter cookie visibility to scripts, or change how the browser sends the cookie.