CRLF Injection Affecting h2 package, versions [,4.3.0)
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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- published27 Aug 2025
- disclosed25 Aug 2025
- creditsebastianosrt
Introduced: 25 Aug 2025
NewCVE-2025-57804 (opens in a new tab)How to fix?
Upgrade h2 to version 4.3.0 or higher.
Overview
h2 is a Pure-Python HTTP/2 protocol implementation
Affected versions of this package are vulnerable to CRLF Injection due to insufficient validation in the request headers. This occurs when servers downgrade HTTP/2 requests to HTTP/1.1 without properly validating header names/values, enabling attackers to manipulate request boundaries and bypass security controls.