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Fencer Intel
high 7.5

CVE-2016-8740 in the critical feed json

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 restric…

published 2016-12-05 9 y ago modified 2026-06-17 4 mo ago also EUVD-2016-9575

cvss
7.5
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
79.1%
EPSS 79.1% chance of exploitation in 30 days, percentile 99.6%
public exploits
1
Exploit-DB

Summary

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.

Patch / fix

  • apache2 Debian 14, Debian 13, Debian 12 2.4.25-1

debian advisories DEBIAN-CVE-2016-8740

  • httpd24-httpd RHEL 2 SOFTWARE_COLLECTIONS 2.4.25-9.el6
  • httpd24-httpd RHEL 2 SOFTWARE_COLLECTIONS 2.4.25-9.el7
  • httpd24-mod_ssl RHEL 2 SOFTWARE_COLLECTIONS 1:2.4.25-9.el6
  • httpd24-mod_ssl RHEL 2 SOFTWARE_COLLECTIONS 1:2.4.25-9.el7
  • httpd24-mod_ldap RHEL 2 SOFTWARE_COLLECTIONS 2.4.25-9.el6
  • httpd24-mod_ldap RHEL 2 SOFTWARE_COLLECTIONS 2.4.25-9.el7
  • httpd24-httpd-tools RHEL 2 SOFTWARE_COLLECTIONS 2.4.25-9.el6
  • httpd24-httpd-tools RHEL 2 SOFTWARE_COLLECTIONS 2.4.25-9.el7

red hat advisories RHSA-2017:1161RHSA-2017:1414RHSA-2017:1413

  • apache2 SLES for SAP 12 SP2, SLES for Raspberry Pi 12 SP2, SLES 12 SP2 +1 more 2.4.23-16.3

suse advisories SUSE-SU-2017:0203-1

  • apache2 openSUSE Tumbleweed 2.4.49-1.1

opensuse advisories openSUSE-SU-2024:10623-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2016-8740 updated cvss 5.9

httpd: Incomplete handling of LimitRequestFields directive in mod_http2

  • Red Hat JBoss Core Services
    fixed: vendor fix RHSA-2017:1415
  • Red Hat JBoss Core Services on RHEL 6 Server jbcs-httpd24-httpd 2.4.23-120.jbcs.el6, jbcs-httpd24-openssl 1.0.2h-13.jbcs.el6, jbcs-httpd24-mod_ssl 2.4.23-120.jbcs.el6, jbcs-httpd24-mod_ldap 2.4.23-120.jbcs.el6, jbcs-httpd24-httpd-libs 2.4.23-120.jbcs.el6, jbcs-httpd24-httpd-tools 2.4.23-120.jbcs.el6, +7 more
    fixed: vendor fix RHSA-2017:1414
  • Red Hat JBoss Core Services on RHEL 7 Server jbcs-httpd24-httpd 2.4.23-120.jbcs.el7, jbcs-httpd24-openssl 1.0.2h-13.jbcs.el7, jbcs-httpd24-mod_ssl 2.4.23-120.jbcs.el7, jbcs-httpd24-mod_ldap 2.4.23-120.jbcs.el7, jbcs-httpd24-httpd-libs 2.4.23-120.jbcs.el7, jbcs-httpd24-httpd-tools 2.4.23-120.jbcs.el7, +7 more
    fixed: vendor fix RHSA-2017:1413
  • Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 6) httpd24-httpd 2.4.25-9.el6, httpd24-mod_ssl 2.4.25-9.el6, httpd24-mod_ldap 2.4.25-9.el6, httpd24-httpd-tools 2.4.25-9.el6, httpd24-mod_session 2.4.25-9.el6, httpd24-httpd-manual 2.4.25-9.el6, +1 more Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 7) httpd24-httpd 2.4.25-9.el7, httpd24-mod_ssl 2.4.25-9.el7, httpd24-mod_ldap 2.4.25-9.el7, httpd24-httpd-tools 2.4.25-9.el7, httpd24-mod_session 2.4.25-9.el7, httpd24-httpd-manual 2.4.25-9.el7, +1 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 6.7) httpd24-httpd 2.4.25-9.el6, httpd24-mod_ssl 2.4.25-9.el6, httpd24-mod_ldap 2.4.25-9.el6, httpd24-httpd-tools 2.4.25-9.el6, httpd24-mod_session 2.4.25-9.el6, httpd24-httpd-manual 2.4.25-9.el6, +1 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.3) httpd24-httpd 2.4.25-9.el7, httpd24-mod_ssl 2.4.25-9.el7, httpd24-mod_ldap 2.4.25-9.el7, httpd24-httpd-tools 2.4.25-9.el7, httpd24-mod_session 2.4.25-9.el7, httpd24-httpd-manual 2.4.25-9.el7, +1 more Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 6) httpd24-httpd 2.4.25-9.el6, httpd24-mod_ssl 2.4.25-9.el6, httpd24-mod_ldap 2.4.25-9.el6, httpd24-httpd-tools 2.4.25-9.el6, httpd24-mod_session 2.4.25-9.el6, httpd24-httpd-manual 2.4.25-9.el6, +1 more Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 7) httpd24-httpd 2.4.25-9.el7, httpd24-mod_ssl 2.4.25-9.el7, httpd24-mod_ldap 2.4.25-9.el7, httpd24-httpd-tools 2.4.25-9.el7, httpd24-mod_session 2.4.25-9.el7, httpd24-httpd-manual 2.4.25-9.el7, +1 more
    fixed: vendor fix RHSA-2017:1161
  • Red Hat Directory Server 8 httpd Red Hat Enterprise Linux 5 httpd Red Hat Enterprise Linux 6 httpd, mod_ssl, httpd-tools, httpd-manual Red Hat Enterprise Linux 7 httpd, mod_ssl, mod_ldap, httpd-tools, mod_session, httpd-manual, +1 more Red Hat JBoss Enterprise Application Platform 5 httpd Red Hat JBoss Enterprise Application Platform 6 httpd, mod_ssl, mod_ldap, httpd-tools, httpd-manual, httpd22 httpd22
    +3 more products
    Red Hat JBoss Enterprise Web Server 1 httpd Red Hat JBoss Enterprise Web Server 2 jbcs-httpd24, httpd22 httpd22, jbcs-httpd24-runtime Red Hat JBoss Web Server 3 httpd24
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Timeline

  1. Published
  2. First public exploit (EDB-40909)

Exploit prediction

79.07% chance of exploitation in the next 30 days, higher than 99.6% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • EDB-40909 Apache 2.4.23 mod_http2 - Denial of Service dos, 2016-12-12
  • packetstormsecurity.com http://packetstormsecurity.com/files/140023/Apache-HTTPD-Web-Server-2.4.23-Memory-Exhaustion.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.0 7.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • Apache Software Foundation Apache HTTP Server

Classification

Weakness
  • CWE-20 Improper Input Validation
  • CWE-399 Resource Management Errors
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.