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Twisted SSH client and server deny of service during SSH handshake.

High severity GitHub Reviewed Published Mar 3, 2022 in twisted/twisted • Updated Sep 4, 2023

Package

pip twisted (pip)

Affected versions

>= 21.7.0, < 22.2.0

Patched versions

22.2.0

Description

Impact

The Twisted SSH client and server implementation naively accepted an infinite amount of data for the peer's SSH version identifier.

A malicious peer can trivially craft a request that uses all available memory and crash the server, resulting in denial of service. The attack is as simple as nc -rv localhost 22 < /dev/zero.

Patches

The issue was fix in GitHub commit twisted/twisted@98387b3

A fix is available in Twisted 22.2.0.

Workarounds

  • Limit access to the SSH server only to trusted source IP addresses.
  • Connect over SSH only to trusted destination IP addresses.

References

Reported at https://twistedmatrix.com/trac/ticket/10284
Discussions at GHSA-rv6r-3f5q-9rgx

For more information

Found by vin01

References

@adiroiban adiroiban published to twisted/twisted Mar 3, 2022
Published to the GitHub Advisory Database Mar 3, 2022
Reviewed Mar 3, 2022
Published by the National Vulnerability Database Mar 3, 2022
Last updated Sep 4, 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
None
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:N/A:H

EPSS score

0.384%
(73rd percentile)

Weaknesses

CVE ID

CVE-2022-21716

GHSA ID

GHSA-rv6r-3f5q-9rgx

Source code

Credits

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