Skip to content

Regular Expression Denial of Service in websocket-extensions (NPM package)

high severity Published Jun 5, 2020 in faye/websocket-extensions-node • Updated Aug 25, 2021

Package

npm websocket-extensions (npm)

Affected versions

< 0.1.4

Patched versions

0.1.4

Description

Impact

The ReDoS flaw allows an attacker to exhaust the server's capacity to process
incoming requests by sending a WebSocket handshake request containing a header
of the following form:

Sec-WebSocket-Extensions: a; b="\c\c\c\c\c\c\c\c\c\c ...

That is, a header containing an unclosed string parameter value whose content is
a repeating two-byte sequence of a backslash and some other character. The
parser takes exponential time to reject this header as invalid, and this will
block the processing of any other work on the same thread. Thus if you are
running a single-threaded server, such a request can render your service
completely unavailable.

Patches

Users should upgrade to version 0.1.4.

Workarounds

There are no known work-arounds other than disabling any public-facing
WebSocket functionality you are operating.

References

References

@jcoglan jcoglan published the maintainer security advisory Jun 2, 2020

CVE ID

CVE-2020-7662

CVSS Score

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