CVE-2026-48859

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 OTP 29.0.2, corresponding to ssh from 6.0 before 6.0.1.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

References

• https://github.com/erlang/otp/security/advisories/GHSA-3w6p-vwhf-wvp4 ↗
• https://cna.erlef.org/cves/CVE-2026-48859.html ↗
• https://osv.dev/vulnerability/EEF-CVE-2026-48859 ↗
• https://www.erlang.org/doc/system/versions.html#order-of-versions ↗
• https://github.com/erlang/otp/commit/c342092ef4b369bb409d5b71ac8fd83bab74aedf ↗