CVE-2021-31618
Published: 15 June 2021
Apache HTTP Server protocol handler for the HTTP/2 protocol checks received request headers against the size limitations as configured for the server and used for the HTTP/1 protocol as well. On violation of these restrictions and HTTP response is sent to the client with a status code indicating why the request was rejected. This rejection response was not fully initialised in the HTTP/2 protocol handler if the offending header was the very first one received or appeared in a a footer. This led to a NULL pointer dereference on initialised memory, crashing reliably the child process. Since such a triggering HTTP/2 request is easy to craft and submit, this can be exploited to DoS the server. This issue affected mod_http2 1.15.17 and Apache HTTP Server version 2.4.47 only. Apache HTTP Server 2.4.47 was never released.
Notes
| Author | Note |
|---|---|
| mdeslaur | per upstream advisory, "This issue affected mod_http2 1.15.17 and Apache HTTP Server version 2.4.47 only. Apache HTTP Server 2.4.47 was never released." seems introduced by: https://github.com/apache/httpd/commit/a4fba223668c554e06bc78d6e3a88f33d4238ae4 Not sure the Debian patch in 2.4.46-5 is right, need to investigate |
Priority
Status
| Package | Release | Status |
|---|---|---|
|
apache2 Launchpad, Ubuntu, Debian |
bionic |
Not vulnerable
|
| focal |
Not vulnerable
|
|
| groovy |
Not vulnerable
|
|
| hirsute |
Not vulnerable
|
|
| impish |
Not vulnerable
|
|
| jammy |
Not vulnerable
|
|
| trusty |
Not vulnerable
|
|
| upstream |
Released
(2.4.46-5)
|
|
| xenial |
Not vulnerable
|
|
|
Patches: upstream: https://github.com/apache/httpd/commit/f990e5ecad40b100a8a5c7c1033c46044a9cb244 upstream: http://svn.apache.org/viewvc?view=revision&revision=1889759 upstream: https://svn.apache.org/viewvc/httpd/httpd/branches/2.4.x/modules/http2/h2_stream.c?r1=1889759&r2=1889758&pathrev=1889759 |
||
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score | 7.5 |
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality | None |
| Integrity impact | None |
| Availability impact | High |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |