request for large response leads to denial of service
CVE: CVE-2019-9517
Component: HTTP/2
CWE: CWE-400
Severity: Important
CVSS v3: 7.5/CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Release date: 2019-08-13T00:00:00+00:00

A vulnerability was found in HTTP/2. An attacker can open a HTTP/2 window so the peer can send without constraint. The TCP window remains closed so the peer cannot write the bytes on the wire. The attacker then sends a stream of requests for a large response object. Depending on how the server's queue is setup, the responses can consume excess memory, CPU, or both, potentially leading to a denial of service. The highest threat from this vulnerability is to system availability.

Statement: The package httpd versions as shipped with Red Hat Enterprise Linux 5, 6 and 7 are not affected by this issue as HTTP/2 support is not provided.
This flaw has no available mitigation for nodejs package. It will be updated once the available fixes are released for Red Hat Enterprise Linux and Red Hat Software Collections.

The nodejs RPM shipped in OpenShift Container Platform 3.9 and 3.10 is not affected by this flaw as it does not contain the vulnerable code.

Remediation:
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

For the update to take effect, all services linked to the OpenSSL library must be restarted, or the system rebooted. After installing the updated packages, the httpd daemon will be restarted automatically.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the updated packages, the httpd daemon will be restarted automatically.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

For the update to take effect, all services linked to the OpenSSL library must be restarted, or the system rebooted. After installing the updated packages, the httpd daemon will be restarted automatically.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the updated packages, the httpd daemon will be restarted automatically.
Before applying the update, back up your existing installation, including all applications, configuration files, databases and database settings, and so on.

The References section of this erratum contains a download link (you must log in to download the update).
Before applying the update, back up your existing installation, including all applications, configuration files, databases and database settings, and so on.

The References section of this erratum contains a download link (you must log in to download the update).
Before applying the update, back up your existing installation, including all applications, configuration files, databases and database settings, and so on.

Installation instructions are available from the Fuse 7.6.0 product documentation page:
https://access.redhat.com/documentation/en-us/red_hat_fuse/7.6/
The httpd version shipped with Red Hat Enterprise Linux 8 provides HTTP/2 support through mod_http2 package. While mod_http2 package is not updated, users can disable HTTP/2 support as mitigation action by executing the following steps:

1. Stop httpd service:
$ systemctl stop httpd

2. Remove http/2 protocol support from configuration files:
$ sed -i 's/\(h2\)\|\(h2c\)//g' <httpd_config_file>

3. Validate configuration files to make sure all syntax is valid:
$ apachectl configtest

4. Restart httpd service:
$ systemctl start httpd