CVE-2026-49975

HIGH LAB

Apache HTTP Server: mod_http2 denial of service

Title source: cna
STIX 2.1

Exploitation Summary

EIP tracks 15 public exploits for CVE-2026-49975. PoCs published by Unclecheng-li, mrx-arafat, fevar54.

AI-analyzed exploit summary This repository contains a functional Python-based PoC for CVE-2026-49975, an HTTP/2 Bomb vulnerability that exploits HPACK index-reference amplification combined with HTTP/2 flow-control stalling to trigger memory exhaustion on vulnerable servers. The exploit sends crafted HTTP/2 frames to induce excessive memory allocation and stall responses, leading to a denial-of-service condition.

Description

Memory Allocation with Excessive Size Value vulnerability in Apache HTTP Server's mod_http leads to denial of service via malicious HTTP requests. This issue affects Apache HTTP Server: from 2.4.17 through 2.4.67.

Exploits (15)

github WORKING POC 587 stars
by Unclecheng-li · cpoc
https://github.com/Unclecheng-li/poc-lab/tree/main/CVE-2026-49975 HTTP2 Bomb

This repository contains a functional Python-based PoC for CVE-2026-49975, an HTTP/2 Bomb vulnerability that exploits HPACK index-reference amplification combined with HTTP/2 flow-control stalling to trigger memory exhaustion on vulnerable servers. The exploit sends crafted HTTP/2 frames to induce excessive memory allocation and stall responses, leading to a denial-of-service condition.

Classification
Working Poc 95%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: Multiple HTTP/2 implementations (nginx, Apache httpd, Microsoft IIS, Envoy, Cloudflare Pingora)
No auth needed
Prerequisites: Target must support HTTP/2 · Attacker must be able to establish an HTTP/2 connection to the target
mistral-large-3 · analyzed Jun 11, 2026 Full analysis →
nomisec WORKING POC 7 stars
by mrx-arafat · poc
https://github.com/mrx-arafat/CVE-2026-49975-POC

This repository contains a functional proof-of-concept exploit for CVE-2026-49975, an HTTP/2 denial-of-service vulnerability. The exploit leverages HPACK indexed references and flow-control window manipulation to exhaust server memory, targeting vulnerabilities in nginx, Apache httpd, Envoy, and other HTTP/2 implementations.

Classification
Working Poc 100%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: HTTP/2 servers (nginx < 1.29.8, Apache httpd < 2.4.67, Envoy < 1.37.2, etc.)
No auth needed
Prerequisites: HTTP/2 support on target server · Network connectivity to target
mistral-large-3 · analyzed Jun 08, 2026 Full analysis →
nomisec WORKING POC 5 stars
by fevar54 · poc
https://github.com/fevar54/Proof-of-Concept-POC---CVE-2026-49975-HTTP-2-Bomb-

This repository contains a functional proof-of-concept exploit for CVE-2026-49975, an HTTP/2 Bomb vulnerability that combines HPACK Bomb and Slowloris-style techniques to cause a denial-of-service (DoS) by consuming server memory. The exploit includes a Python script that crafts malicious HTTP/2 frames to trigger the vulnerability, along with detection scripts and a Docker lab for testing.

Classification
Working Poc 95%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: nginx < 1.29.8, Apache httpd < mod_http2 v2.0.41, Microsoft IIS, Envoy, Cloudflare Pingora
No auth needed
Prerequisites: Target server with HTTP/2 enabled · Network connectivity to the target
mistral-large-3 · analyzed Jun 08, 2026 Full analysis →
github WRITEUP 3 stars
by LSG-PolarBear · poc
https://github.com/LSG-PolarBear/CVE-2026-49975

This repository provides a detailed technical explanation of CVE-2026-49975, an HTTP/2 vulnerability affecting major web servers like Apache, nginx, and Envoy. It describes the attack mechanism combining HPACK compression bombs and window stalling to cause memory exhaustion and DoS.

Classification
Writeup 90%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: Apache, nginx, Envoy, IIS (HTTP/2 implementations)
No auth needed
Prerequisites: HTTP/2 enabled on target server · Network access to target
mistral-large-3 · analyzed Jun 10, 2026 Full analysis →
nomisec SCANNER 2 stars
by mindcodings · poc
https://github.com/mindcodings/http2-bomb-detector

This repository contains a non-destructive detection script for CVE-2026-49975, an HTTP/2 HPACK compression bomb vulnerability affecting Nginx and Apache httpd. The script sends minimal probe requests (refs=3) to analyze server responses and determine vulnerability status without causing denial-of-service.

Classification
Scanner 98%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: Nginx (< 1.29.8), Apache httpd (2.4.17 – 2.4.67 with mod_http2 < 2.0.41)
No auth needed
Prerequisites: HTTP/2 support on target server · Direct network access to target port (typically 443)
mistral-large-3 · analyzed Jul 03, 2026 Full analysis →
nomisec SCANNER 1 stars
by adminlove520 · poc
https://github.com/adminlove520/http2-bomb-detector

This repository contains a non-destructive detection script for CVE-2026-49975, an HTTP/2 Bomb vulnerability affecting Nginx and Apache httpd. It sends minimal probe packets to analyze server responses and determine vulnerability status without causing actual harm.

Classification
Scanner 95%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: Nginx < 1.29.8, Apache httpd 2.4.17-2.4.67 (mod_http2 < 2.0.41)
No auth needed
Prerequisites: HTTP/2 support on target server · TLS/SSL connectivity
mistral-large-3 · analyzed Jun 13, 2026 Full analysis →
nomisec WRITEUP 1 stars
by minc-nice-100 · poc
https://github.com/minc-nice-100/http2-bomb-analysis-paper

This repository contains a detailed technical analysis of CVE-2026-49975, an HTTP/2 Bomb vulnerability affecting major web servers. It explains the attack mechanism, including HPACK indexed-reference amplification and flow-control window stalling, and provides in-depth analysis of the vulnerability's impact and mitigation strategies.

Classification
Writeup 100%
Attack Type
Dos
Complexity
Complex
Reliability
Reliable
Target: nginx, Apache httpd, Microsoft IIS, Envoy Proxy, Cloudflare Pingora
No auth needed
Prerequisites: HTTP/2 support on target server · Ability to send crafted HTTP/2 frames
mistral-large-3 · analyzed Jun 13, 2026 Full analysis →
nomisec WORKING POC 1 stars
by obrige · poc
https://github.com/obrige/http2-bomb

This repository contains a functional HTTP/2 stream amplification PoC targeting CVE-2026-49975, which exploits memory exhaustion via crafted HEADERS frames with excessive internal references. The tool includes a web interface for launching attacks and monitoring results.

Classification
Working Poc 95%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: HTTP/2 servers (Envoy, Apache httpd, Nginx)
No auth needed
Prerequisites: Target server supporting HTTP/2
mistral-large-3 · analyzed Jun 08, 2026 Full analysis →
github WORKING POC
by Manisso · pythonpoc
https://github.com/Manisso/http2-bomb

This PoC exploits CVE-2026-49975, a memory exhaustion vulnerability in Apache HTTP Server's mod_http2 module. The attack combines HPACK header amplification with HTTP/2 stream retention to rapidly deplete server memory by forcing excessive allocations in the HPACK compression tables and maintaining open streams indefinitely.

Classification
Working Poc 98%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: Apache HTTP Server 2.4.17 through 2.4.67 (mod_http2 module)
No auth needed
Prerequisites: Target must support HTTP/2 over TLS · Target must be running a vulnerable version of Apache HTTP Server with mod_http2 enabled · Attacker needs network access to the target server
mistral-large-3 · analyzed Jul 06, 2026 Full analysis →
github WORKING POC
by 0xc03307b · poc
https://github.com/0xc03307b/CVE-2026-49975

This repository contains a functional exploit PoC for CVE-2026-49975, a DoS vulnerability in Apache HTTP Server's HTTP/2 handling. The exploit uses HPACK-encoded headers to force excessive memory allocation during cookie header merging, combined with flow control to delay responses and sustain memory consumption.

Classification
Working Poc 100%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: Apache HTTP Server 2.4.17 to 2.4.67
No auth needed
Prerequisites: HTTP/2 support enabled on target server · Network access to target server
mistral-large-3 · analyzed Jun 18, 2026 Full analysis →
github WORKING POC
by razureink · pythonpoc
https://github.com/razureink/cve-2026-49975-http2bomb_reproduction

This repository contains a functional Python-based PoC for CVE-2026-49975, an HTTP/2 Bomb DoS vulnerability. It exploits HPACK indexed reference bombs combined with flow-control window stalling to exhaust server memory.

Classification
Working Poc 95%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: HTTP/2 servers (nginx < 1.29.8, Apache httpd < 2.4.67, Envoy, IIS, Cloudflare Pingora)
No auth needed
Prerequisites: TLS/ALPN support for HTTP/2 · vulnerable HTTP/2 server implementation
mistral-large-3 · analyzed Jun 13, 2026 Full analysis →
nomisec SCANNER
by wlor0623 · poc
https://github.com/wlor0623/http2-bomb-detector

This repository contains a non-destructive detection script for CVE-2026-49975, an HTTP/2 HPACK compression memory exhaustion vulnerability affecting Nginx and Apache httpd. The tool sends minimal probe requests (refs=3) to analyze server responses and determine vulnerability status without causing denial of service.

Classification
Scanner 98%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: Nginx (< 1.29.8), Apache httpd (2.4.17 – 2.4.67 with mod_http2 < 2.0.41)
No auth needed
Prerequisites: HTTP/2 enabled on target server · Direct network access to target port (typically 443)
mistral-large-3 · analyzed Jul 18, 2026 Full analysis →
github WORKING POC
by LiaoZiqi-GZFLS · pythonpoc
https://github.com/LiaoZiqi-GZFLS/CVE-2026-49975

This repository contains a functional HTTP/2 denial-of-service exploit for CVE-2026-49975, leveraging HPACK compression bombs, slowloris flow control, and cookie fragmentation to exhaust server memory. The PoC includes both an attack script and a vulnerable test server for validation.

Classification
Working Poc 95%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: Apache httpd (<2.0.41), nginx (<1.29.8), Envoy (<1.37.3), Microsoft IIS, Cloudflare Pingora
No auth needed
Prerequisites: HTTP/2 support on target server · Python 3.x with h2/hpack/hyperframe libraries
mistral-large-3 · analyzed Jun 10, 2026 Full analysis →
nomisec WRITEUP
by qpzmalqp · poc
https://github.com/qpzmalqp/CVE-2026-49975

This repository provides a detailed technical explanation of CVE-2026-49975, an HTTP/2 vulnerability affecting major web servers like Apache, nginx, and Envoy. It describes the attack mechanism combining HPACK compression bombs and window stalling to cause memory exhaustion and DoS.

Classification
Writeup 90%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: Apache, nginx, Envoy, IIS (HTTP/2 implementations)
No auth needed
Prerequisites: HTTP/2 support on target server · ability to send crafted HTTP/2 requests
mistral-large-3 · analyzed Jun 10, 2026 Full analysis →
github SCANNER
by renzi25031469 · shellpoc
https://github.com/renzi25031469/CVE-2026-49975-HTTP-2-Bomb

This repository contains a detection script for CVE-2026-49975, which identifies HTTP/2-enabled servers and flags potential exposure to the 'HTTP/2 Bomb' vulnerability. It does not exploit the vulnerability but scans for affected software versions and HTTP/2 support.

Classification
Scanner 100%
Attack Type
Dos
Complexity
Moderate
Reliability
Reliable
Target: nginx, Apache httpd, Microsoft IIS, Envoy, Cloudflare Pingora
No auth needed
Prerequisites: HTTP/2-enabled server · curl with HTTP/2 support
mistral-large-3 · analyzed Jun 08, 2026 Full analysis →

Scores

CVSS v3 7.5
EPSS 0.2798
EPSS Percentile 97.9%
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 poc
Automatable yes
Technical Impact partial

Lab Environment

COMMUNITY SUSPICIOUS
Community Lab
docker pull ghcr.io/obrige/http2-bomb:latest
docker pull httpd:2.4.67
+12 more repos

Details

CWE
CWE-409 CWE-789
Status published
Products (4)
apache/http_server 2.4.17 - 2.4.68
Apache Software Foundation/Apache HTTP Server 2.4.17 - 2.4.67
debian/debian_linux 11.0
f5/nginx < 1.29.8
Published Jun 08, 2026
Tracked Since Jun 08, 2026