mod_proxy: SSRF via a crafted request uri-path containing "unix:"
CVE: CVE-2021-40438
Component: httpd
CWE: CWE-918
Severity: Important
CVSS v3: 8.9/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Release date: 2021-09-16T00:00:00+00:00

A Server-Side Request Forgery (SSRF) flaw was found in mod_proxy of httpd. This flaw allows a remote, unauthenticated attacker to make the httpd server forward requests to an arbitrary server. The attacker could get, modify, or delete resources on other services that may be behind a firewall and inaccessible otherwise. The impact of this flaw varies based on what services and resources are available on the httpd network.

Statement: Impact of the flaw set to Important because the actions an attacker can do varies a lot based on the kind of infrastructure in place, the kind of internal services and resources, and the available endpoints on those services. The attacker should also perform some kind of target-specific reconnaissance in order to find out all the above information.

The version of httpd as shipped in Red Hat Enterprise Linux 7 is affected by this flaw even if the upstream code was not, because the Unix Domain Socket support required to trigger the flaw was backported.
The version of httpd as shipped in Red hat Enterprise Linux 6 is not affected by this flaw because there is no support for Unix Domain Socket.

The flaw can be triggered only if mod_proxy is in use (e.g. ProxyPass, ReverseProxy is used in the httpd configuration files).

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

After installing the updated packages, the httpd daemon will be restarted automatically.
Before applying this update, make sure all previously released errata relevant to your system have been applied.

For details on how to apply this update, refer to:

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

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

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 for the update. You must be logged in to download the update.
Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.