CVE-2026-27135

HIGH

nghttp2 Denial of service: Assertion failure due to the missing state validation

Title source: cna
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2026-27135. PoCs published by Zmo247.

AI-analyzed exploit summary This repository provides a patch and build scripts for CVE-2026-27135 affecting nghttp2 on Debian. It includes a Docker-based solution to compile and replace the vulnerable library with a hardened version of nghttp2 v1.65.0.

Description

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 `nghttp2_session_terminate_session` or `nghttp2_session_terminate_session2` 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 FRAME_SIZE_ERROR causes assertion failure. nghttp2 v1.68.1 adds missing state validation to avoid assertion failure. No known workarounds are available.

Exploits (1)

nomisec WRITEUP
by Zmo247 · poc
https://github.com/Zmo247/nghttp2-cve-2026-27135-patch

This repository provides a patch and build scripts for CVE-2026-27135 affecting nghttp2 on Debian. It includes a Docker-based solution to compile and replace the vulnerable library with a hardened version of nghttp2 v1.65.0.

Classification
Writeup 95%
Attack Type
Other
Complexity
Moderate
Reliability
Reliable
Target: nghttp2 <= 1.64.0-1.1 on Debian 13 (Trixie)
No auth needed
Prerequisites: Docker environment · access to build and deploy images
devstral-2 · analyzed Apr 09, 2026 Full analysis →

Scores

CVSS v3 7.5
EPSS 0.0056
EPSS Percentile 42.0%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CISA SSVC

Vulnrichment
Exploitation none
Automatable yes
Technical Impact partial

Details

CWE
CWE-617
Status published
Products (1)
nghttp2/nghttp2 < 1.68.1 (2 CPE variants)
Published Mar 18, 2026
Tracked Since Mar 19, 2026