CRLF Injection Affecting undici package, versions <6.27.0>=7.0.0 <7.28.0>=8.0.0 <8.5.0
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-17372658
- published18 Jun 2026
- disclosed17 Jun 2026
- creditByunSuyoung
Introduced: 17 Jun 2026
NewCVE-2026-9679 (opens in a new tab)How to fix?
Upgrade undici to version 6.27.0, 7.28.0, 8.5.0 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 CRLF Injection in the parseSetCookie. An attacker can inject arbitrary HTTP headers by supplying specially crafted percent-encoded values in the Set-Cookie header, which are improperly decoded and then forwarded into response headers. This can enable actions such as session fixation, open redirect, or cache poisoning.
Note: This is only exploitable if the application parses Set-Cookie headers using the affected function and then forwards the parsed value into a response header without proper sanitization.
Workaround
This vulnerability can be mitigated by sanitizing the values returned by the affected cookie parsing functions to strip or reject CR, LF, NUL, ;, and = bytes before forwarding them into response headers.