Improper Handling of Case Sensitivity Affecting fastify package, versions >=5.12.2 <5.12.6
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-FASTIFY-20883333
- published13 Oct 2026
- disclosed13 Oct 2026
- creditUttej Badwane, kian0417
Introduced: 13 Oct 2026
NewCVE-2026-107832 (opens in a new tab)How to fix?
Upgrade fastify to version 5.12.6 or higher.
Overview
fastify is an overhead web framework, for Node.js.
Affected versions of this package are vulnerable to Improper Handling of Case Sensitivity via the lowerCaseHeadersSchema function in lib/validation.js, when a headers schema uses propertyNames with an enum or const constraint. Because header name values inside propertyNames were not lowercased during schema normalization, an attacker can bypass header validation by supplying header names in mixed or upper case that match the enum/const values as authored but not as normalized, causing the validation to incorrectly reject or accept requests.