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 29.0.2 corresponding to ssh from 6.0 before 6.0.1.
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History
Wed, 10 Jun 2026 17:30:00 +0000
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ssvc
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Wed, 10 Jun 2026 16:00:00 +0000
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| Description | 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 29.0.2 corresponding to ssh from 6.0 before 6.0.1. | |
| Title | SSH server timing side-channel in ssh_auth:check_password/3 allows unauthenticated username enumeration | |
| First Time appeared |
Erlang
Erlang erlang\/otp |
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| Weaknesses | CWE-208 | |
| CPEs | cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:* | |
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Erlang
Erlang erlang\/otp |
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cvssV4_0
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Status: PUBLISHED
Assigner: EEF
Published:
Updated: 2026-06-10T16:19:43.145Z
Reserved: 2026-05-25T20:44:10.697Z
Link: CVE-2026-48859
Updated: 2026-06-10T16:19:38.063Z
Status : Received
Published: 2026-06-10T16:17:12.373
Modified: 2026-06-10T16:17:12.373
Link: CVE-2026-48859
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OpenCVE Enrichment
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