CVE-2016-8740
published 2016-12-05CVE-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 request-header…
PriorityP266high7.5CVSS 3.0
AVNACLPRNUINSUCNINAH
EXPLOIT
EPSS
79.07%
99.6th percentile
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.
Affected
12 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| apache | http_server | — | — |
| apache | http_server | — | — |
| apache | http_server | — | — |
| apache | http_server | — | — |
| apache | http_server | — | — |
| apache | http_server | — | — |
| apache | http_server | — | — |
| apache_software_foundation | apache_http_server | — | — |
| apple | macos_high_sierra | — | — |
| apple | macos_high_sierra_10.13.1_security_update_2017-001_sierra_and_security_update_20 | — | — |
| apple | macos_sierra_10.12.4_security_update_2017-001_el_capitan_and_security_update_201 | — | — |
| debian | apache2 | < apache2 2.4.25-1 (bookworm) | apache2 2.4.25-1 (bookworm) |
Detection & IOCsextracted from sources · hover to see the quote
bytes↗
HEADERS frame: \x82\x84\x86\x41\x86\xa0\xe4\x1d\x13\x9d\x09\x7a\x88\x25\xb6\x50\xc3\xab\xb6\x15\xc1\x53\x03\x2a\x2f\x2a\x40\x83\x18\xc6\x3f\x04\x76\x76\x76\x76
bytes↗
CONTINUATION frame: \x40\x83\x18\xc6\x3f\x04\x76\x76\x76\x76
- →Detect exploit by looking for HTTP/2 connection preface 'PRI * HTTP/2.0' followed by an unbounded stream of CONTINUATION frames (frame type 0x09) on a single Stream ID without END_HEADERS flag being set, indicating memory exhaustion attempt. ↗
- →CONTINUATION frames in the exploit carry frame type byte 0x09 with flags 0x01 and stream ID 0x00000001 in an infinite loop — alert on high-volume CONTINUATION frames (type=0x09) on the same stream without END_HEADERS. ↗
- →Vulnerable servers are those with 'h2' or 'h2c' listed in the Protocols directive; detection should focus on Apache 2.4.17–2.4.23 with HTTP/2 enabled. ↗
- →Monitor server memory consumption for rapid exhaustion correlated with HTTP/2 connections; the exploit causes unbounded memory growth via repeated CONTINUATION frames carrying header block fragments. ↗
- →Incomplete handling of LimitRequestFields in mod_http2 is the root cause; alert on httpd processes with abnormally growing RSS when serving HTTP/2 traffic. ↗
- ·The vulnerability only affects Apache HTTP Server when the Protocols directive includes 'h2' or 'h2c'; servers running only http/1.1 are not affected. ↗
- ·Temporary mitigation is to disable HTTP/2 by removing h2 and h2c from the Protocols directive, leaving only 'Protocols http/1.1'. ↗
- ·Affected version range is Apache HTTP Server 2.4.17 through 2.4.23 only; versions outside this range are not impacted by this specific CVE. ↗
CVSS provenance
nvdv3.07.5HIGHCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvdv2.05.0MEDIUMAV:N/AC:L/Au:N/C:N/I:N/A:P
osv7.5HIGH
vendor_debian7.5HIGH
vendor_redhat7.5HIGH
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Apple
CVE-2016-8740: macOS High Sierra 10.13.1, Security Update 2017-001 Sierra, and Security Update 2017-004 El Capitan
vendor_apple·2017-10-31·CVSS 7.5
CVE-2016-8740 [HIGH] CVE-2016-8740: macOS High Sierra 10.13.1, Security Update 2017-001 Sierra, and Security Update 2017-004 El Capitan
Apple Security Update: About the security content of macOS High Sierra 10.13.1, Security Update 2017-001 Sierra, and Security Update 2017-004 El Capitan
Product: macOS High Sierra 10.13.1, Security Update 2017-001 Sierra, and Security Update 2017-004 El Capitan
CVE: CVE-2016-8740
Component: CVE-2016-8740
Apple
CVE-2016-8740: macOS High Sierra 10.13
vendor_apple·2017-09-25·CVSS 7.5
CVE-2016-8740 [HIGH] CVE-2016-8740: macOS High Sierra 10.13
Apple Security Update: About the security content of macOS High Sierra 10.13
Product: macOS High Sierra
Version: 10.13
CVE: CVE-2016-8740
Component: CVE-2016-8740
Apple
CVE-2016-8740: macOS Sierra 10.12.4, Security Update 2017-001 El Capitan, and Security Update 2017-001 Yosemite
vendor_apple·2017-03-27·CVSS 7.5
CVE-2016-8740 [HIGH] CVE-2016-8740: macOS Sierra 10.12.4, Security Update 2017-001 El Capitan, and Security Update 2017-001 Yosemite
Apple Security Update: About the security content of macOS Sierra 10.12.4, Security Update 2017-001 El Capitan, and Security Update 2017-001 Yosemite
Product: macOS Sierra 10.12.4, Security Update 2017-001 El Capitan, and Security Update 2017-001 Yosemite
CVE: CVE-2016-8740
Component: CVE-2016-8740
Red Hat
httpd: Incomplete handling of LimitRequestFields directive in mod_http2
vendor_redhat·2016-12-04·CVSS 7.5
CVE-2016-8740 [HIGH] CWE-20 httpd: Incomplete handling of LimitRequestFields directive in mod_http2
httpd: Incomplete handling of LimitRequestFields directive in mod_http2
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.
A vulnerability was found in httpd's handling of the LimitRequestFields directive in mod_http2, affecting servers with HTTP/2 enabled. An attacker could send crafted requests with headers larger than the server's available memory, causing httpd to crash.
Statement: Red Hat Product Security has rated this issue as having Low security
impact. This issue is not currently planned to be addressed in future
updates. For additiona
Debian
CVE-2016-8740: apache2 - The mod_http2 module in the Apache HTTP Server 2.4.17 through 2.4.23, when the P...
vendor_debian·2016·CVSS 7.5
CVE-2016-8740 [HIGH] CVE-2016-8740: apache2 - The mod_http2 module in the Apache HTTP Server 2.4.17 through 2.4.23, when the P...
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.
Scope: local
bookworm: resolved (fixed in 2.4.25-1)
bullseye: resolved (fixed in 2.4.25-1)
forky: resolved (fixed in 2.4.25-1)
sid: resolved (fixed in 2.4.25-1)
trixie: resolved (fixed in 2.4.25-1)
GHSA
GHSA-pfj2-72r3-p693: The mod_http2 module in the Apache HTTP Server 2
ghsa_unreviewed·2022-05-13
CVE-2016-8740 [HIGH] CWE-20 GHSA-pfj2-72r3-p693: The mod_http2 module in the Apache HTTP Server 2
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.
OSV
CVE-2016-8740: The mod_http2 module in the Apache HTTP Server 2
osv·2016-12-05·CVSS 7.5
CVE-2016-8740 [HIGH] CVE-2016-8740: The mod_http2 module in the Apache HTTP Server 2
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.
No detection rules found.
Hackernews
New HTTP/2 Bomb Vulnerability Allows Remote DoS on NGINX, Apache, IIS, Envoy & Cloudflare
blogs_hackernews·2026-06-03·CVSS 7.5
CVE-2016-6581 [HIGH] New HTTP/2 Bomb Vulnerability Allows Remote DoS on NGINX, Apache, IIS, Envoy & Cloudflare
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## New HTTP/2 Bomb Vulnerability Allows Remote DoS on NGINX, Apache, IIS, Envoy & Cloudflare
Cybersecurity researchers have discovered a remote denial-of-service exploit that affects major web servers, including NGINX, Apache HTTPD, Microsoft IIS, Envoy, and Cloudflare Pingora.
The vulnerability has been codenamed HTTP/2 Bomb by Calif.
"The vulnerable behavior exists in each server's default HTTP/2 configuration," the company said, adding it was discovered by OpenAI Codex by chaining together two known techniques: a compression bomb and a Slowloris -style hold.
"The bomb targets HPACK, HTTP/2's header compression scheme: one
Tenable
[R5] SecurityCenter 5.4.3 Fixes Multiple Vulnerabilities
blogs_tenable·2017-02-14
[R5] SecurityCenter 5.4.3 Fixes Multiple Vulnerabilities
## Cloud Exposure
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Tenable CIEM Request a demo
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## Vulnerability Exposure
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Tenable Security Center Request a demo
Tenable Web App Scanning Try for free
Tenable Patch Management Request a demo
Tenable Enclave Security Request a demo
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## AI Exposure
Tenable AI Exposure Request a demo
## OT/IoT Exposure
Tenable OT Security Request a demo
## Identity Exposure
Tenable Identity Exposure Request a demo
## Business needs
Active Directory
AI Security Posture Management (AI-SPM)
AWS security
Azure security
Cloud Security Posture Man
Bugzilla
CVE-2016-8740 httpd: Incomplete handling of LimitRequestFields directive in mod_http2
bugzilla·2016-12-05·CVSS 7.5
CVE-2016-8740 [HIGH] CVE-2016-8740 httpd: Incomplete handling of LimitRequestFields directive in mod_http2
CVE-2016-8740 httpd: Incomplete handling of LimitRequestFields directive in mod_http2
The HTTP/2 protocol implementation (mod_http2) had an incomplete handling of the LimitRequestFields directive. This allowed an attacker to inject unlimited request headers into the server, leading to eventual memory exhaustion.
Affects all versions from 2.4.17 to 2.4.23.
Mitigation:
As a temporary workaround - HTTP/2 can be disabled by changing
the configuration by removing h2 and h2c from the Protocols
line(s) in the configuration file.
The resulting line should read:
Protocols http/1.1
External References:
https://httpd.apache.org/security/vulnerabilities_24.html
http://seclists.org/bugtraq/2016/Dec/3
Discussion:
Created httpd tracking bugs for this issue:
Affects: fedora-all [bug 1401530]
-
Bugzilla
CVE-2016-8740 httpd: Incomplete handling of LimitRequestFields directive in mod_http2 [fedora-all]
bugzilla·2016-12-05·CVSS 7.5
CVE-2016-8740 [HIGH] CVE-2016-8740 httpd: Incomplete handling of LimitRequestFields directive in mod_http2 [fedora-all]
CVE-2016-8740 httpd: Incomplete handling of LimitRequestFields directive in mod_http2 [fedora-all]
This is an automatically created tracking bug! It was created to ensure
that one or more security vulnerabilities are fixed in affected versions
of Fedora.
For comments that are specific to the vulnerability please use bugs filed
against the "Security Response" product referenced in the "Blocks" field.
For more information see:
http://fedoraproject.org/wiki/Security/TrackingBugs
When submitting as an update, use the fedpkg template provided in the next
comment(s). This will include the bug IDs of this tracking bug as well as
the relevant top-level CVE bugs.
Please also mention the CVE IDs being fixed in the RPM changelog and the
fedpkg commit message.
NOTE: this issue affects multiple s
http://packetstormsecurity.com/files/140023/Apache-HTTPD-Web-Server-2.4.23-Memory-Exhaustion.htmlhttp://rhn.redhat.com/errata/RHSA-2017-1415.htmlhttp://www.securityfocus.com/bid/94650http://www.securitytracker.com/id/1037388https://access.redhat.com/errata/RHSA-2017:1161https://access.redhat.com/errata/RHSA-2017:1413https://access.redhat.com/errata/RHSA-2017:1414https://github.com/apache/httpd/commit/29c63b786ae028d82405421585e91283c8fa0da3https://h20566.www2.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03725en_ushttps://lists.apache.org/thread.html/56c2e7cc9deb1c12a843d0dc251ea7fd3e7e80293cde02fcd65286ba%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/84a3714f0878781f6ed84473d1a503d2cc382277e100450209231830%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/r04e89e873d54116a0635ef2f7061c15acc5ed27ef7500997beb65d6f%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/r476d175be0aaf4a17680ef98c5153b4d336eaef76fb2224cc94c463a%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/r76142b8c5119df2178be7c2dba88fde552eedeec37ea993dfce68d1d%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/r9f93cf6dde308d42a9c807784e8102600d0397f5f834890708bf6920%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rb14daf9cc4e28d18cdc15d6a6ca74e565672fabf7ad89541071d008b%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rc998b18880df98bafaade071346690c2bc1444adaa1a1ea464b93f0a%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rcc44594d4d6579b90deccd4536b5d31f099ef563df39b094be286b9e%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rd18c3c43602e66f9cdcf09f1de233804975b9572b0456cc582390b6f%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rd336919f655b7ff309385e34a143e41c503e133da80414485b3abcc9%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/re1e3a24664d35bcd0a0e793e0b5fc6ca6c107f99a1b2c545c5d4b467%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/re3d27b6250aa8548b8845d314bb8a350b3df326cacbbfdfe4d455234%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rf6449464fd8b7437704c55f88361b66f12d5b5f90bcce66af4be4ba9%40%3Ccvs.httpd.apache.org%3Ehttps://security.gentoo.org/glsa/201701-36https://security.netapp.com/advisory/ntap-20180423-0001/https://support.apple.com/HT208221https://www.exploit-db.com/exploits/40909/https://www.tenable.com/security/tns-2017-04http://packetstormsecurity.com/files/140023/Apache-HTTPD-Web-Server-2.4.23-Memory-Exhaustion.htmlhttp://rhn.redhat.com/errata/RHSA-2017-1415.htmlhttp://www.securityfocus.com/bid/94650http://www.securitytracker.com/id/1037388https://access.redhat.com/errata/RHSA-2017:1161https://access.redhat.com/errata/RHSA-2017:1413https://access.redhat.com/errata/RHSA-2017:1414https://github.com/apache/httpd/commit/29c63b786ae028d82405421585e91283c8fa0da3https://h20566.www2.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03725en_ushttps://lists.apache.org/thread.html/56c2e7cc9deb1c12a843d0dc251ea7fd3e7e80293cde02fcd65286ba%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/84a3714f0878781f6ed84473d1a503d2cc382277e100450209231830%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/r04e89e873d54116a0635ef2f7061c15acc5ed27ef7500997beb65d6f%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/r476d175be0aaf4a17680ef98c5153b4d336eaef76fb2224cc94c463a%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/r76142b8c5119df2178be7c2dba88fde552eedeec37ea993dfce68d1d%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/r9f93cf6dde308d42a9c807784e8102600d0397f5f834890708bf6920%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rb14daf9cc4e28d18cdc15d6a6ca74e565672fabf7ad89541071d008b%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rc998b18880df98bafaade071346690c2bc1444adaa1a1ea464b93f0a%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rcc44594d4d6579b90deccd4536b5d31f099ef563df39b094be286b9e%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rd18c3c43602e66f9cdcf09f1de233804975b9572b0456cc582390b6f%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rd336919f655b7ff309385e34a143e41c503e133da80414485b3abcc9%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/re1e3a24664d35bcd0a0e793e0b5fc6ca6c107f99a1b2c545c5d4b467%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/re3d27b6250aa8548b8845d314bb8a350b3df326cacbbfdfe4d455234%40%3Ccvs.httpd.apache.org%3Ehttps://lists.apache.org/thread.html/rf6449464fd8b7437704c55f88361b66f12d5b5f90bcce66af4be4ba9%40%3Ccvs.httpd.apache.org%3Ehttps://security.gentoo.org/glsa/201701-36https://security.netapp.com/advisory/ntap-20180423-0001/https://support.apple.com/HT208221https://www.exploit-db.com/exploits/40909/https://www.tenable.com/security/tns-2017-04
2016-12-05
Published