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

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

https://cvefeed.io/rssfeed/latest.atom / Wed, 06/10/2026 - 20:28
CVE ID :CVE-2026-48859
Published : June 10, 2026, 4:17 p.m. | 18 minutes ago
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.
Severity: 6.3 | MEDIUM
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