Authentication Bypass by Capture-replay Affecting com.sshtools:maverick-synergy-client package, versions [,3.1.0)


Severity

0.0
medium
0
10

    Threat Intelligence

    Exploit Maturity
    Proof of concept
    EPSS
    96.17% (100th percentile)

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  • Snyk ID SNYK-JAVA-COMSSHTOOLS-6596921
  • published 11 Apr 2024
  • disclosed 18 Dec 2023
  • credit Fabian Bäumer, Marcus Brinkmann, Jörg Schwenk

How to fix?

Upgrade com.sshtools:maverick-synergy-client to version 3.1.0 or higher.

Overview

com.sshtools:maverick-synergy-client is a Next Generation Java SSH API

Affected versions of this package are vulnerable to Authentication Bypass by Capture-replay during the establishment of the secure channel. An attacker can manipulate handshake sequence numbers to delete messages sent immediately after the channel is established.

Note:

  1. Sequence numbers are only validated once the channel is established and arbitrary messages are allowed during the handshake, allowing them to manipulate the sequence numbers.

  2. The potential consequences of the general Terrapin attack are dependent on the messages exchanged after the handshake concludes. If you are using a custom SSH service and do not resort to the authentication protocol, you should check that dropping the first few messages of a connection does not yield security risks.

Impact:

While cryptographically novel, there is no discernable impact on the integrity of SSH traffic beyond giving the attacker the ability to delete the message that enables some features related to keystroke timing obfuscation. To successfully carry out the exploitation, the connection needs to be protected using either the ChaCha20-Poly1305 or CBC with Encrypt-then-MAC encryption methods. The attacker must also be able to intercept and modify the connection's traffic.

Workaround

Temporarily disable the affected chacha20-poly1305@openssh.com encryption and *-etm@openssh.com MAC algorithms in the affected configuration, and use unaffected algorithms like AES-GCM instead.

CVSS Scores

version 3.1
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Snyk

5.9 medium
  • Attack Vector (AV)
    Network
  • Attack Complexity (AC)
    High
  • Privileges Required (PR)
    None
  • User Interaction (UI)
    None
  • Scope (S)
    Unchanged
  • Confidentiality (C)
    None
  • Integrity (I)
    High
  • Availability (A)
    None
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NVD

5.9 medium
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Red Hat

5.9 medium
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SUSE

5.9 medium