CVE-2021-31618

2021-06-1500:00:00

ubuntu.com

7.5 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

5 Medium

CVSS2

Access Vector

NETWORK

Access Complexity

LOW

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

PARTIAL

AV:N/AC:L/Au:N/C:N/I:N/A:P

0.01 Low

EPSS

Percentile

83.1%

JSON

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.

Bugs

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