Permissive List of Allowed Inputs 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-17372758
- published18 Jun 2026
- disclosed17 Jun 2026
- creditUnknown
Introduced: 17 Jun 2026
NewCVE-2026-11525 (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 Permissive List of Allowed Inputs via permissive substring matching in the Set-Cookie attribute parsing. An attacker can weaken cookie SameSite enforcement by crafting a response with a non-standard SameSite value that is interpreted as a more permissive setting, potentially allowing cookies to be sent in cross-site requests.
Note: This is only exploitable if the application consumes Set-Cookie headers from server responses (for example via undici's fetch or proxy code paths) and then forwards or relies on the parsed sameSite attribute.
Workaround
This vulnerability can be mitigated by validating that the parsed sameSite attribute is exactly 'Strict', 'Lax', or 'None' (case-insensitive) before relying on or forwarding it.