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Mallory
HighPublic exploit

Apache HTTP Server mod_http2 CONTINUATION Frame Memory Exhaustion DoS

IdentifiersCVE-2016-8740CWE-400

CVE-2016-8740 is a denial-of-service flaw in Apache HTTP Server's mod_http2 module affecting versions 2.4.17 through 2.4.23 when HTTP/2 is enabled via the Protocols directive including h2 or h2c. In the vulnerable implementation, request-header length is not properly restricted during processing of HTTP/2 CONTINUATION frames. A remote client can send crafted HTTP/2 requests containing excessive or effectively unbounded header continuation data, causing the server to allocate memory without adequate limits. The issue is specifically tied to handling of CONTINUATION frames in an HTTP/2 request and results in resource exhaustion rather than code execution.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

A remote unauthenticated attacker can cause denial of service by driving excessive memory consumption in Apache httpd processes handling HTTP/2 traffic. Successful exploitation can degrade performance, exhaust available memory, and render the service unavailable to legitimate users. The provided context characterizes this as an HTTP/2 Slowloris-style exhaustion issue associated with endless or crafted CONTINUATION frames.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, disable HTTP/2 support in Apache HTTP Server by removing h2/h2c from the Protocols configuration so mod_http2 is not exposed. More generally, restrict exposure of HTTP/2 services, place the server behind infrastructure that can enforce request/header limits, and monitor for abnormal memory growth or abusive HTTP/2 connections.

Remediation

Patch, then assume compromise.

Upgrade Apache HTTP Server to a fixed release newer than the affected range 2.4.17 through 2.4.23. Apply the vendor-provided mod_http2/httpd updates that enforce appropriate limits on HTTP/2 request-header processing and CONTINUATION frame handling.
PUBLIC EXPLOITS

Exploits

No valid public exploits. Mallory filtered out 1 candidate as fakes, detection scripts, or README-only repos.

VALID 0 / 1 TOTALView more in app

All candidate exploits were filtered out by Mallory's validation.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
Apache Software FoundationHttp Serverapplication

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What this page doesn’t show

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Exposure mapping

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Threat actor evidence

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Associated malware

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Detection signatures

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Vendor-by-vendor mapping

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Social activity

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