Vulnerability · Published Jun 10, 2026 · Assigned by EEF
CVE-2026-48859SSH server timing side-channel in ssh_auth:check_password/3 allows unauthenticated username enumeration
Medium 6.3
In plain English
A medium-severity security flaw in OTP from Erlang. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 29% of all known vulnerabilities).
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu:25.10 | erlang | no fix listed | UBUNTU-CVE-2026-48859 |
Affected products (as reported)
Weakness: CWE-208 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
References
- https://github.com/erlang/otp/security/advisories/GHSA-3w6p-vwhf-wvp4 vendor-advisory, related
- https://cna.erlef.org/cves/CVE-2026-48859.html related
- https://osv.dev/vulnerability/EEF-CVE-2026-48859 related
- https://www.erlang.org/doc/system/versions.html#order-of-versions x_version-scheme
- https://github.com/erlang/otp/commit/c342092ef4b369bb409d5b71ac8fd83bab74aedf patch