CVE-2026-9679
June 17, 2026, 8:20 p.m.
5.9
Medium
Description
Impact:
undici's cookie parser in parseSetCookie percent-decodes cookie values via qsUnescape, turning encoded sequences like %0D%0A, %00, %3B, and %3D into their literal byte equivalents. RFC 6265 §5.4 does not specify any decoding and browsers do not decode either.
Applications that parse a Set-Cookie header and then forward the parsed value into a response header (proxies, middleware, SSR frameworks) become vulnerable to HTTP response header injection: an attacker-controlled upstream can inject arbitrary Set-Cookie, Location, or Cache-Control headers into the application's downstream response, enabling session fixation, open redirect, or cache poisoning.
Affected applications are those that use undici's cookie parsing (parseSetCookie, parseCookie, getSetCookies) and forward the parsed cookie value into a response header.
This was introduced in undici 7.0.0 via PR #3789.
Patches:
Upgrade to undici v6.26.0, v7.28.0 or v8.5.0.
Workarounds:
If upgrade is not immediately possible, do not forward values returned by parseSetCookie/parseCookie/getSetCookies directly into response headers; sanitize the value first to strip or reject CR, LF, NUL, ;, and = bytes.
Product(s) Impacted
| Vendor | Product | Versions |
|---|---|---|
| Undici |
|
|
Weaknesses
Common security weaknesses mapped to this vulnerability.
CWE-93
Improper Neutralization of CRLF Sequences ('CRLF Injection')
The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.
*CPE(s)
Affected systems and software identified for this CVE.
| Type | Vendor | Product | Version | Update | Edition | Language | Software Edition | Target Software | Target Hardware | Other Information |
|---|---|---|---|---|---|---|---|---|---|---|
| a | undici | undici | <7.0.0 | / | / | / | / | / | / | / |
| a | undici | undici | 6.26.0 | / | / | / | / | / | / | / |
| a | undici | undici | 7.28.0 | / | / | / | / | / | / | / |
| a | undici | undici | 8.5.0 | / | / | / | / | / | / | / |
Tags
CVSS Score
CVSS Data - 3.1
- Attack Vector: NETWORK
- Attack Complexity: HIGH
- Privileges Required: NONE
- Scope: UNCHANGED
- Confidentiality Impact: NONE
- Integrity Impact: HIGH
- Availability Impact: NONE
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Timeline
Published: June 17, 2026, 6:18 p.m.
Last Modified: June 17, 2026, 8:20 p.m.
Last Modified: June 17, 2026, 8:20 p.m.
Status : Awaiting Analysis
CVE has been marked for Analysis. Normally once in this state the CVE will be analyzed by NVD staff within 24 hours.
More infoSource
ce714d77-add3-4f53-aff5-83d477b104bb
*Disclaimer: Some vulnerabilities do not have an associated CPE. To enhance the data, we use AI to infer CPEs based on CVE details. This is an automated process and might not always be accurate.