Public proof of conceptFix available

CVE-2016-8740

A public proof of concept exists; no exploitation attested.

Published2016-12-05
WeaknessCWE-20 · CWE-399

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

The mod_http2 module in the Apache HTTP Server 2.4.17 through 2.4.23, when the Protocols configuration includes h2 or h2c, does not restrict request-header length, which allows remote attackers to cause a denial of service (memory consumption) via crafted CONTINUATION frames in an HTTP/2 request.

Timeline

dates in UTC

2016-12-0519:59CVE publishedNVD
2026-10-2319:23First public proof of conceptPoC-in-GitHub
2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2016-8740?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2016-8740?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Apache HTTP Server

Branch	Affected	Fixed in	Source
2.4	= 2.4.17	no fix published	NVD
2.4	= 2.4.18	no fix published	NVD
2.4	= 2.4.19	no fix published	NVD
2.4	= 2.4.20	no fix published	NVD
2.4	= 2.4.21	no fix published	NVD
2.4	= 2.4.22	no fix published	NVD
2.4	= 2.4.23	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

github.comPatch

Detection

read 2026-10-23 19:23 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 2 repositories, unverifiedlcfpadilha/mac0352-ep4jptr218/apachedos

Sources

NVDCVSS 3.07.5read 2026-10-23
NVDCVSS 2.05read 2026-10-23
NVDweakness (CWE)CWE-20, CWE-399read 2026-10-23
FIRST EPSSEPSS score79.1 %read 2026-10-23
PoC-in-GitHubproof of concept2read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published: 2016-12-05
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2016-8740?

Is CVE-2016-8740 actively exploited?

Active exploitation of CVE-2016-8740 has not been confirmed. Its EPSS score was 79.1% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2016-8740?

CVE-2016-8740 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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