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Http Server CVE-2026-49975

| EUVDEUVD-2026-35105 HIGH
Memory Allocation with Excessive Size Value (CWE-789)
2026-06-03 GHSA-262v-g5h9-6mc6
Denial Of Service Apache Debian Nginx Debian Linux Http Server F5
7.5
CVSS 3.1 · Vendor
View

Vulnerability Assessment

Weakness
CWE
CWE-789
ASVS 5.0
V15 - Secure Coding and Architecture Memory allocation limits
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv4 – Jun 09, 2026

Denial of service in Apache HTTP Server 2.4.17 through 2.4.67 (via the bundled mod_http2 module) allows remote unauthenticated attackers to exhaust server memory by sending crafted HTTP/2 requests whose cookie headers are not correctly counted against LimitRequestFields. Publicly available exploit code exists and a third-party write-up describes a 'hidden HTTP/2 bomb,' but EPSS exploitation probability is currently very low (0.02%, 5th percentile) and the CVE is not on the CISA KEV list.

Earlier versions of this analysis (3)
v3 Jun 09, 2026 - 17:30 cvss changed CVSS 7.5

Denial of service in Apache HTTP Server's mod_http2 module (versions 2.4.17 through 2.4.67) allows remote unauthenticated attackers to exhaust server memory by sending malicious HTTP/2 requests that trigger excessive memory allocation. The flaw stems from incorrect cookie header accounting against the LimitRequestFields directive, enabling attackers to bypass the configured header limit. Publicly available exploit code exists and a vendor patch has been released, though EPSS exploitation probability is currently low at 0.02%.

v2 Jun 03, 2026 - 16:01

Remote denial-of-service in Apache httpd's mod_http2 (and several other HTTP/2 implementations including nginx, Microsoft IIS, Envoy, and Cloudflare Pingora) allows an unauthenticated attacker to exhaust server memory by combining an HPACK indexed-reference bomb with an HTTP/2 zero-window flow-control stall. Publicly available exploit code exists in the form of the disclosed fix commits and a detailed third-party writeup, which the original reporters note can be turned into a working exploit by capable AI models; against Apache httpd a single low-bandwidth client can pin roughly 32 GB of server memory in about 18 seconds. CVE-2026-49975 specifically tracks the Apache httpd instance of this class, fixed in mod_http2 version 2.0.41.

v1 Jun 03, 2026 - 15:40

Memory exhaustion via HTTP/2 cookie-header fragmentation ('HTTP/2 Bomb') affects Apache httpd, nginx, Microsoft IIS, Envoy, and Cloudflare Pingora, enabling remote denial-of-service by unauthenticated clients. The attack exploits the absence of a per-request header-count cap: an attacker fragments a large cookie into thousands of HTTP/2 header crumbs across multiple persistent streams, pinning server memory for the lifetime of each connection at near-zero client cost. No patch is yet available for Microsoft IIS, Envoy, or Pingora; nginx 1.29.8 and Apache mod_http2 v2.0.41 contain fixes, and the fix commits are public, with the oss-security advisory noting that AI tooling can trivially convert them into working exploits against remaining unpatched implementations.

Affected VersionsENISA

Apache HTTP Server 2.4.17 ≤2.4.67

Affected Packages

euvd apache_http_server no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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Severity by source

Vendor (CNA) PRIMARY 7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SUSE HIGH
Red Hat 7.5 HIGH

Primary rating from Vendor (CNA).

CVSS VectorVendor

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

1
CVSS changed
Jun 09, 2026 - 17:22 NVD
7.5 (HIGH)

Description PRE-NVD

Disclosed via oss-security. NVD scoring and full description are pending.

Executive ViewAI

Why It Matters

Apache HTTP Server versions 2.4.17 through 2.4.67 contain a denial-of-service vulnerability in the bundled mod_http2 module that allows unauthenticated remote attackers to exhaust server memory through specially crafted HTTP/2 requests. Organizations running these versions face potential service unavailability; publicly available exploit code exists, requiring urgent remediation to protect service availability.

Recommended Action

24 hours: Identify all systems running Apache HTTP Server 2.4.17-2.4.67 in production and non-production environments. 7 days: Apply vendor-released patch to update to Apache 2.4.68 or later across all affected systems. 30 days: Validate complete patch deployment through inventory verification and automated scanning to confirm zero vulnerable instances remain operational.

Business Impact: High
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.0%
Top 95% exploitable
Exploit
POC
Public exploit code exists
Data Quality
8 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment Fortinet MSRC Vendor GitHub VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC Yes
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
High
Technical Impact
Partial

Priority Score

58
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +38
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

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Same weakness CWE-789 – Memory Allocation with Excessive Size Value

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Vendor StatusVendor

SUSE

Severity: High
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Module for Basesystem 15 SP7 Fixed
SUSE Linux Enterprise Module for Package Hub 15 SP7 Fixed
SUSE Linux Enterprise Module for Server Applications 15 SP7 Fixed

References

Advisories & patches
PATCH https://github.com/apache/httpd/commit/47d3100b252dc6668a9e46ae885242be9eeca9cd PATCH https://github.com/nginx/nginx/commit/365694160a85229a7cb006738de9260d49ff5fa2 ADVISORY https://access.redhat.com/errata/RHSA-2026:25042 ADVISORY https://access.redhat.com/errata/RHSA-2026:25057 ADVISORY https://access.redhat.com/errata/RHSA-2026:25090 ADVISORY https://blog.calif.io/p/codex-discovered-a-hidden-http2-bomb ADVISORY https://fortiguard.fortinet.com/psirt/FG-IR-26-163 ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-49975 ADVISORY https://seclists.org/oss-sec/2026/q2/790 ADVISORY https://seclists.org/oss-sec/2026/q2/845 ADVISORY https://ubuntu.com/security/notices/USN-8398-2 ADVISORY https://vuldb.com/vuln/368279 REF http://www.openwall.com/lists/oss-security/2026/06/03/3 REF http://www.openwall.com/lists/oss-security/2026/06/08/16 REF https://access.redhat.com/errata/RHSA-2026:25225 REF https://access.redhat.com/errata/RHSA-2026:27114 REF https://access.redhat.com/errata/RHSA-2026:27200 REF https://access.redhat.com/errata/RHSA-2026:27201 REF https://access.redhat.com/errata/RHSA-2026:36373 REF https://access.redhat.com/errata/RHSA-2026:36831 REF https://access.redhat.com/errata/RHSA-2026:36846 REF https://access.redhat.com/errata/RHSA-2026:50538 REF https://access.redhat.com/errata/RHSA-2026:50572 REF https://access.redhat.com/errata/RHSA-2026:55930 REF https://access.redhat.com/errata/RHSA-2026:55992 REF https://access.redhat.com/security/cve/CVE-2026-49975 REF https://bugzilla.redhat.com/show_bug.cgi?id=2485371 REF https://github.com/EQSTLab/CVE-2026-49975 REF https://httpd.apache.org/security/vulnerabilities_24.html REF https://lists.debian.org/debian-lts-announce/2026/06/msg00009.html REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49975.json

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