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NVD / CVE Program· CNA apache

CVE-2016-8740: 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…

HighCVSS 7.5 · v3.0—Proof of concept Fix available

Noroxi assessment

Priority: Plan (action score 54/100)

  • Public proof-of-concept code exists (Exploit-DB, GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 79% (FIRST EPSS); higher than 99.6% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: apache2 (Debian:12) 2.4.25-1; apache2 (openSUSE:Tumbleweed) 2.4.49-1.1; jbcs-httpd24-httpd (Red Hat:jboss_core_services:1::el6) 0:2.4.23-120.jbcs.el6.

Add it to your regular patch cycle. Upgrade to apache2 (Debian:12) 2.4.25-1; apache2 (openSUSE:Tumbleweed) 2.4.49-1.1; jbcs-httpd24-httpd (Red Hat:jboss_core_services:1::el6) 0:2.4.23-120.jbcs.el6 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published
Dec 5, 2016
Updated
Jun 16, 2026
EPSS
79.0% · 99th percentile

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JSON

Action score

54

Plan

Add it to your regular patch cycle.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
24 / 30 · 79.0%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • Proof of concept exists, no weaponized module
  • A fix has been released

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

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VendorProduct
apachehttp server

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When you'll hear from us

  • when a new CVE affecting this product is published
  • when a record in your stack enters KEV or is weaponized

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits every 10 minutes on paid plans, on the hour on the free plan.

Is Apache HTTP Server on your server exposed to the internet?Run a port scan

Your free account also gets you

  • CVE alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools, at most 30 a day (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

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Free account, no card. Unfollow any time.

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (apache). Independent of NVD's CPE analysis and usually ahead of it.

  • Apache Software Foundation Apache HTTP Server

    • 2.4.17 - 2.4.23affected
Affected versions · NVD (7)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • apache http server2.4.17
  • apache http server2.4.18
  • apache http server2.4.19
  • apache http server2.4.20
  • apache http server2.4.21
  • apache http server2.4.22
  • apache http server2.4.23

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12apache2before 2.4.25-12.4.25-1
openSUSE:Tumbleweedapache2before 2.4.49-1.12.4.49-1.1
Red Hat:jboss_core_services:1::el6jbcs-httpd24-httpdbefore 0:2.4.23-120.jbcs.el60:2.4.23-120.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-httpd-debuginfobefore 0:2.4.23-120.jbcs.el60:2.4.23-120.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-httpd-develbefore 0:2.4.23-120.jbcs.el60:2.4.23-120.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-httpd-libsbefore 0:2.4.23-120.jbcs.el60:2.4.23-120.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-httpd-manualbefore 0:2.4.23-120.jbcs.el60:2.4.23-120.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-httpd-selinuxbefore 0:2.4.23-120.jbcs.el60:2.4.23-120.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-httpd-toolsbefore 0:2.4.23-120.jbcs.el60:2.4.23-120.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-mod_ldapbefore 0:2.4.23-120.jbcs.el60:2.4.23-120.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-mod_proxy_htmlbefore 1:2.4.23-120.jbcs.el61:2.4.23-120.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-mod_securitybefore 0:2.9.1-19.GA.jbcs.el60:2.9.1-19.GA.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-mod_security-debuginfobefore 0:2.9.1-19.GA.jbcs.el60:2.9.1-19.GA.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-mod_sessionbefore 0:2.4.23-120.jbcs.el60:2.4.23-120.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-mod_sslbefore 1:2.4.23-120.jbcs.el61:2.4.23-120.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-opensslbefore 1:1.0.2h-13.jbcs.el61:1.0.2h-13.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-openssl-debuginfobefore 1:1.0.2h-13.jbcs.el61:1.0.2h-13.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-openssl-develbefore 1:1.0.2h-13.jbcs.el61:1.0.2h-13.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-openssl-libsbefore 1:1.0.2h-13.jbcs.el61:1.0.2h-13.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-openssl-perlbefore 1:1.0.2h-13.jbcs.el61:1.0.2h-13.jbcs.el6
Red Hat:jboss_core_services:1::el6jbcs-httpd24-openssl-staticbefore 1:1.0.2h-13.jbcs.el61:1.0.2h-13.jbcs.el6
Red Hat:jboss_core_services:1::el7jbcs-httpd24-httpdbefore 0:2.4.23-120.jbcs.el70:2.4.23-120.jbcs.el7
Red Hat:jboss_core_services:1::el7jbcs-httpd24-httpd-debuginfobefore 0:2.4.23-120.jbcs.el70:2.4.23-120.jbcs.el7
Red Hat:jboss_core_services:1::el7jbcs-httpd24-httpd-develbefore 0:2.4.23-120.jbcs.el70:2.4.23-120.jbcs.el7

+35

Same product

apache: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-42013Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)KEV
    99Now
  • CVE-2021-41773Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49KEV
    99Now
  • CVE-2024-38475Apache HTTP Server weakness in mod_rewrite when first segment of substitution matches filesystem path.KEV
    96Now

Published before and after this one in the same product

  • ← EarlierCVE-2016-4979Jul 6, 2016 · The Apache HTTP Server 2.4.18 through 2.4.20, when mod_http2 and mod_ssl are enabled, does not properly recognize the "SSLVerifyClient…
    36Monitor
  • ← EarlierCVE-2016-5387Jul 18, 2016 · The Apache HTTP Server through 2.4.23 follows RFC 3875 section 4.1.18 and therefore does not protect applications from the presence of…
    49Plan
  • Later →CVE-2017-3167Jun 19, 2017 · In Apache httpd 2.2.x before 2.2.33 and 2.4.x before 2.4.26, use of the ap_get_basic_auth_pw() by third-party modules outside of the…
    45Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:apache22.4.25-1 · Debian:12Package registry (OSV)
opensuse:apache22.4.49-1.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:httpd24-httpd0:2.4.25-9.el6 · Red Hat:rhel_software_collections:2::el6Package registry (OSV)
red hat:httpd24-httpd-debuginfo0:2.4.25-9.el6 · Red Hat:rhel_software_collections:2::el6Package registry (OSV)
red hat:httpd24-httpd-devel0:2.4.25-9.el6 · Red Hat:rhel_software_collections:2::el6Package registry (OSV)
red hat:httpd24-httpd-manual0:2.4.25-9.el6 · Red Hat:rhel_software_collections:2::el6Package registry (OSV)
red hat:httpd24-httpd-tools0:2.4.25-9.el6 · Red Hat:rhel_software_collections:2::el6Package registry (OSV)
red hat:httpd24-mod_ldap0:2.4.25-9.el6 · Red Hat:rhel_software_collections:2::el6Package registry (OSV)
red hat:httpd24-mod_proxy_html1:2.4.25-9.el6 · Red Hat:rhel_software_collections:2::el6Package registry (OSV)
red hat:httpd24-mod_session0:2.4.25-9.el6 · Red Hat:rhel_software_collections:2::el6Package registry (OSV)
red hat:httpd24-mod_ssl1:2.4.25-9.el6 · Red Hat:rhel_software_collections:2::el6Package registry (OSV)
red hat:jbcs-httpd24-httpd0:2.4.23-120.jbcs.el7 · Red Hat:jboss_core_services:1::el7Package registry (OSV)
red hat:jbcs-httpd24-httpd-debuginfo0:2.4.23-120.jbcs.el7 · Red Hat:jboss_core_services:1::el7Package registry (OSV)
red hat:jbcs-httpd24-httpd-devel0:2.4.23-120.jbcs.el7 · Red Hat:jboss_core_services:1::el7Package registry (OSV)
suse:apache22.4.23-16.3 · SUSE:Linux Enterprise Server for Raspberry Pi 12 SP2Package registry (OSV)

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Exploit-DB entry ×1
  • Proof-of-concept repository on GitHub ×2

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Exploit-DB entrydos2016-12-12
Proof-of-concept repository on GitHubstars:12017-10-11
Proof-of-concept repository on GitHubstars:12021-08-03

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoC+6 d
  3. TodayNov 15, 2026+3631 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Not on record for this CVE: researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-20 · Improper Input Validation

CVSS vector

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

References

Show all references (19 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records