CVE-2016-1546

httpd: mod_http2 denial-of-service by thread starvation

Severity Score

5.9

*CVSS v3

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

*SSVC

Descriptions

The Apache HTTP Server 2.4.17 and 2.4.18, when mod_http2 is enabled, does not limit the number of simultaneous stream workers for a single HTTP/2 connection, which allows remote attackers to cause a denial of service (stream-processing outage) via modified flow-control windows.

El servidor HTTP Apache 2.4.17 y 2.4.18, cuando mod_http2 está activado, no limita el número de trabajadores de flujo simultáneos para una sola conexión HTTP/2, lo que permite a atacantes remotos provocar una denegación de servicio (corte de flujo de procesamiento) a través de las ventanas de control de flujo modificadas.

A denial of service flaw was found in httpd's mod_http2 module. A remote attacker could use this flaw to block server threads for long times, causing starvation of worker threads, by manipulating the flow control windows on streams.

The Apache HTTP Server is a powerful, efficient, and extensible web server. The httpd24 packages provide a recent stable release of version 2.4 of the Apache HTTP Server, along with the mod_auth_kerb module. The httpd24 Software Collection has been upgraded to version 2.4.25, which provides a number of bug fixes and enhancements over the previous version.

*Credits: N/A

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Attack Vector

Network

Attack Complexity

Medium

Authentication

None

Confidentiality

None

Integrity

None

Availability

Partial

* Common Vulnerability Scoring System

SSVC

Decision:-

Exploitation

Automatable

Tech. Impact

* Organization's Worst-case Scenario

Timeline

2016-01-07 CVE Reserved
2016-07-06 CVE Published
2024-08-05 CVE Updated
2025-03-18 EPSS Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-399: Resource Management Errors

CAPEC

References (23)

URL	Tag	Source
http://svn.apache.org/viewvc?view=revision&revision=1733727	X_refsource_confirm
http://www.apache.org/dist/httpd/CHANGES_2.4	X_refsource_confirm
http://www.oracle.com/technetwork/security-advisory/cpuoct2016-2881722.html	X_refsource_confirm
http://www.oracle.com/technetwork/topics/security/bulletinoct2016-3090566.html	X_refsource_confirm
http://www.securityfocus.com/bid/92331	Vdb Entry
https://lists.apache.org/thread.html/56c2e7cc9deb1c12a843d0dc251ea7fd3e7e80293cde02fcd65286ba%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/84a3714f0878781f6ed84473d1a503d2cc382277e100450209231830%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/r04e89e873d54116a0635ef2f7061c15acc5ed27ef7500997beb65d6f%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/r76142b8c5119df2178be7c2dba88fde552eedeec37ea993dfce68d1d%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/r9f93cf6dde308d42a9c807784e8102600d0397f5f834890708bf6920%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/rb14daf9cc4e28d18cdc15d6a6ca74e565672fabf7ad89541071d008b%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/rc998b18880df98bafaade071346690c2bc1444adaa1a1ea464b93f0a%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/rcc44594d4d6579b90deccd4536b5d31f099ef563df39b094be286b9e%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/rd18c3c43602e66f9cdcf09f1de233804975b9572b0456cc582390b6f%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/re1e3a24664d35bcd0a0e793e0b5fc6ca6c107f99a1b2c545c5d4b467%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/re3d27b6250aa8548b8845d314bb8a350b3df326cacbbfdfe4d455234%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/rf6449464fd8b7437704c55f88361b66f12d5b5f90bcce66af4be4ba9%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://security.netapp.com/advisory/ntap-20180601-0001	X_refsource_confirm

URL	Date	SRC

URL	Date	SRC
http://httpd.apache.org/security/vulnerabilities_24.html	2023-11-07

URL	Date	SRC
https://access.redhat.com/errata/RHSA-2017:1161	2023-11-07
https://security.gentoo.org/glsa/201610-02	2023-11-07
https://access.redhat.com/security/cve/CVE-2016-1546	2017-04-26
https://bugzilla.redhat.com/show_bug.cgi?id=1336350	2017-04-26

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Apache Search vendor "Apache"		Http Server Search vendor "Apache" for product "Http Server"				2.4.17 Search vendor "Apache" for product "Http Server" and version "2.4.17"		-		Affected
Apache Search vendor "Apache"		Http Server Search vendor "Apache" for product "Http Server"				2.4.18 Search vendor "Apache" for product "Http Server" and version "2.4.18"		-		Affected