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Regular Expression Denial of Service in websocket-extensions (RubyGem)

High severity GitHub Reviewed Published Jun 2, 2020 in faye/websocket-extensions-ruby • Updated May 16, 2023

Package

bundler websocket-extensions (RubyGems)

Affected versions

< 0.1.5

Patched versions

0.1.5

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 0.1.5.

Workarounds

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

References

References

@jcoglan jcoglan published to faye/websocket-extensions-ruby Jun 2, 2020
Published by the National Vulnerability Database Jun 2, 2020
Reviewed Jun 3, 2020
Published to the GitHub Advisory Database Jun 5, 2020
Last updated May 16, 2023

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

EPSS score

1.647%
(88th percentile)

Weaknesses

CVE ID

CVE-2020-7663

GHSA ID

GHSA-g6wq-qcwm-j5g2

Source code

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