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CVE-2026-48859

CVE-2026-48859 · SSH server timing side-channel in ssh_auth:check_password/3 allows unauthenticated username enumeration

This page contains facts from public vulnerability sources. Check the original advisory before updating.

Observable Timing Discrepancy vulnerability in Erlang/OTP ssh (ssh_auth, ssh_options modules) allows unauthenticated remote username enumeration via timing side-channel in password authentication. When the SSH daemon is configured with the user_passwords or password option, ssh_auth:check_password/3 performs a PBKDF2-SHA256 computation with 600,000 iterations (~300ms) for valid usernames, but returns immediately (~0ms) for invalid usernames via the ssh_options:get_password_option/2 path. This timing difference is detectable in a single authentication attempt and allows an unauthenticated attacker to distinguish valid from invalid usernames. The user_passwords and password options are documented as intended for test purposes; the recommended alternative is pwdfun, which is not affected by this vulnerability. This vulnerability is associated with program files lib/ssh/src/ssh_auth.erl and lib/ssh/src/ssh_options.erl. This issue affects OTP from OTP 29.0 before OTP 29.0.2, corresponding to ssh from 6.0 before 6.0.1.

CVSS 6.3 · Medium · EPSS 0.4% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • erlang

    Versions
    • ≥ 29.0, < 29.0.2: Affected (otp)

    Update to 29.0.2

  • erlang

    Versions
    • ≥ 6.0, < 6.0.1: Affected (otp)

    Update to 6.0.1

  • erlang

    Versions
    • ≥ 032d1bc9491a3975c68faf9bc7776115d6ae3005, < c342092ef4b369bb409d5b71ac8fd83bab74aedf: Affected (git)

    No fix published

  • erlang Ubuntu:25.10

    Versions
    • 1:27.3+dfsg-1ubuntu1
    • 1:27.3+dfsg-1ubuntu1.1
    • 1:27.3.4.1+dfsg-1
    • 1:27.3.4.1+dfsg-1build1
    • 1:27.3.4.1+dfsg-1ubuntu0.1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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