CVE-2026-27135: nghttp2 Denial of service: Assertion failure due to the missing state validation
nghttp2 Denial of service: Assertion failure due to the missing state validation
Other sources
nghttp2 is an implementation of the Hypertext Transfer Protocol version 2 in C. Prior to version 1.68.1, the nghttp2 library stops reading the incoming data when user facing public API nghttp2sessionterminatesession or nghttp2sessionterminatesession2 is called by the application. They might be called internally by the library when it detects the situation that is subject to connection error. Due to the missing internal state validation, the library keeps reading the rest of the data after one of those APIs is called. Then receiving a malformed frame that causes FRAMESIZEERROR causes assertion failure. nghttp2 v1.68.1 adds missing state validation to avoid assertion failure. No known workarounds are available.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
nghttp2to a version that resolves this vulnerability.Fixed in 1.68.1
Event History
Frequently Asked Questions
What is the severity of CVE-2026-27135?
CVE-2026-27135 is classified as a denial-of-service vulnerability due to assertion failure.
How do I fix CVE-2026-27135?
To fix CVE-2026-27135, upgrade the nghttp2 library to version 1.68.1 or later.
What causes CVE-2026-27135?
CVE-2026-27135 is caused by missing state validation in the nghttp2 library when handling incoming data.
Which versions of nghttp2 are affected by CVE-2026-27135?
Versions of nghttp2 prior to 1.68.1 are affected by CVE-2026-27135.
What is nghttp2?
nghttp2 is an implementation of the HTTP/2 protocol in C, which is the library affected by CVE-2026-27135.