Improper Handling of Case Sensitivity Affecting undici package, versions >=7.15.0 <7.30.1>=8.0.0 <8.12.2
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-21181011
- published18 Oct 2026
- disclosed15 Oct 2026
- creditKushal Khemka, Mayank Jangid
Introduced: 15 Oct 2026
NewCVE-2026-109841 (opens in a new tab)How to fix?
Upgrade undici to version 7.30.1, 8.12.2 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 Handling of Case Sensitivity via the fetch() implementation's Subresource Integrity (SRI) verification logic, which matches the algorithm token against a lowercase-only set. A valid but non-lowercase token such as SHA256-... or Sha256-... is treated as unknown and skipped, causing undici to treat the integrity list as empty and accept the response unconditionally. An attacker who controls the response body can therefore deliver arbitrary bytes to an application that pinned a valid uppercase or mixed-case SRI token, with no integrity error raised.
Note: This is only exploitable when the application uses uppercase or mixed-case algorithm tokens (e.g., SHA256, Sha384) in its integrity metadata rather than the canonical lowercase forms.
Workaround
Use lowercase algorithm tokens (sha256, sha384, sha512) in all integrity metadata passed to fetch().