Denial of service when handling HTTP/2 requests in Apache HTTP server

Published: 2016-12-06 01:36:51 | Updated: 2016-12-21 14:56:36
Severity Low
Patch available YES
Number of vulnerabilities 1
CVE ID CVE-2016-8740
Exploitation vector Network
Public exploit Not available
Vulnerable software Apache HTTP Server
Vulnerable software versions Apache HTTP Server 2.4.17
Apache HTTP Server 2.4.18
Apache HTTP Server 2.4.23
Apache HTTP Server 2.4.20
Vendor URL Apache Foundation

Security Advisory

1) Memory leak


The vulnerability allows a remote attacker to cause denial of service.

The vulnerability exists due to improper handling of HTTP/2 headers, when the Protocols configuration includes h2 or h2c. A remote attacker can send a specially crafted HTTP/2 request, containign CONTINUATION frames to vulnerable instance and consume all available memory resources.

Successful exploitation of the vulnerability will result in denial of service (DoS) of affected web server.


On December 20 vendor has issued a new version of Apache HTTP Server 2.4.25 to address this vulnerability.

As a temporary solution it is recommended to limit access to HTTP/2 protocol to trusted IPs only.

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