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.
CVSS breakdown
Affected products
- erlang / erlang/otp
- erlang / erlang/ssh6.0 – 6.0.1
References
- VENDOR_ADVISORYhttps://github.com/erlang/otp/security/advisories/GHSA-3w6p-vwhf-wvp4
- MISChttps://cna.erlef.org/cves/CVE-2026-48859.html
- MISChttps://osv.dev/vulnerability/EEF-CVE-2026-48859
- MISChttps://www.erlang.org/doc/system/versions.html#order-of-versions
- PATCHhttps://github.com/erlang/otp/commit/c342092ef4b369bb409d5b71ac8fd83bab74aedf