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SSH Terrapin attack

Moderate
u3s published GHSA-hx6w-xhph-454x Nov 17, 2025

Package

OTP

Affected versions

>= 17.0

Patched versions

26.2.1, 25.3.2.8, 24.3.4.15, 23.3.4.20, 22.3.4.27
ssh (OTP)
>= 3.0.1
5.1.1, 4.15.3.1, 4.13.2.4, 4.11.1.7, 4.9.1.5

Description

Impact

SSH protocol issue related to initial handshake messages handling.
Potentially, every ssh connection might be impacted.

From terrapin-attack.com:
Terrapin is a prefix truncation attack targeting the SSH protocol. More precisely, Terrapin breaks the integrity of SSH's secure channel. By carefully adjusting the sequence numbers during the handshake, an attacker can remove an arbitrary amount of messages sent by the client or server at the beginning of the secure channel without the client or server noticing it.

Affected/Unaffected Versions

A version larger than or equal to one of the listed patched versions is unaffected; otherwise, a version that satisfies an expression listed under affected versions is affected, and if it does not, it is unaffected.

The documentation of the new OTP version scheme describes how versions should be compared. Note that versions used prior to OTP 17.0, when the new OTP version scheme was introduced, are never listed since it is not well defined how to compare those versions.

In the case of this vulnerability, versions prior to OTP 17.0 are also affected.

Workarounds

n/a

Credits

Thanks to Fabian Bäumer, Marcel Maehren, Marcus Brinkmann, and Jörg Schwenk from the Ruhr University Bochum for finding and responsibly disclosing this vulnerability to the Erlang/OTP project.

References

https://nvd.nist.gov/vuln/detail/cve-2023-48795

Severity

Moderate

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
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

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:H/PR:N/UI:N/S:U/C:N/I:H/A:N

CVE ID

CVE-2023-48795

Weaknesses

Improper Validation of Integrity Check Value

The product does not validate or incorrectly validates the integrity check values or checksums of a message. This may prevent it from detecting if the data has been modified or corrupted in transmission. Learn more on MITRE.