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SYNTHESIS OF THE VULNERABILITY

An attacker can detect if a username is valid by looking at the
pam_ssh prompt.

Severity: 1/4

Consequences: data reading

Provenance: intranet client

Means of attack: no proof of concept, no attack

Ability of attacker: expert (4/4)

Confidence: confirmed by the editor (5/5)

Diffusion of the vulnerable configuration: high (3/3)

Creation date: 01/04/2009

IMPACTED PRODUCTS

– Unix - plateform

DESCRIPTION OF THE VULNERABILITY

The pam_ssh PAM module handles the authentication using the SSH
protocol.

When an attacker enters a valid username, pam_ssh displays "SSH
passphrase". When an attacker enters an invalid username, pam_ssh
displays "Password".

An attacker can therefore use a brute force attack to detect valid
usernames.

CHARACTERISTICS

Identifiers: 263579, 492153, VIGILANCE-VUL-8587

http://vigilance.fr/vulnerability/pam-ssh-user-detection-8587