Authentication Bypass by Capture-replay Affecting russh package, versions <0.40.2
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-RUST-RUSSH-6130674
- published19 Dec 2023
- disclosed18 Dec 2023
- creditFabian Bäumer, Marcus Brinkmann, Jörg Schwenk
Introduced: 18 Dec 2023
CVE-2023-48795 (opens in a new tab)How to fix?
Upgrade russh to version 0.40.2 or higher.
Overview
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:
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.
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.