{"id":"CVE-2026-48859","aliases":["EEF-CVE-2026-48859","EUVD-2026-36054","GHSA-3w6p-vwhf-wvp4","UBUNTU-CVE-2026-48859"],"status":"published","title":"SSH server timing side-channel in ssh_auth:check_password/3 allows unauthenticated username enumeration","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.\n\nWhen 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.\n\nThe user_passwords and password options are documented as intended for test purposes; the recommended alternative is pwdfun, which is not affected by this vulnerability.\n\nThis vulnerability is associated with program files lib/ssh/src/ssh_auth.erl and lib/ssh/src/ssh_options.erl.\n\nThis issue affects OTP from OTP 29.0 before OTP 29.0.2, corresponding to ssh from 6.0 before 6.0.1.","severity":{"version":"4.0","score":6.3,"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00354,"percentile":0.29391,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-208"],"published":"2026-06-10T14:35:43Z","modified":"2026-10-28T02:31:12Z","affected":[{"source":"osv","ecosystem":"Ubuntu:25.10","package":"erlang","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:27.3+dfsg-1ubuntu1","1:27.3+dfsg-1ubuntu1.1","1:27.3.4.1+dfsg-1","1:27.3.4.1+dfsg-1build1","1:27.3.4.1+dfsg-1ubuntu0.1"]}],"products":[{"vendor":"erlang","product":"erlang\\/otp"},{"vendor":"erlang","product":"erlang\\/ssh"},{"vendor":"erlang","product":"otp"}],"references":[{"url":"https://github.com/erlang/otp/security/advisories/GHSA-3w6p-vwhf-wvp4","tags":["vendor-advisory","related","Mitigation","Vendor Advisory","advisory"]},{"url":"https://cna.erlef.org/cves/CVE-2026-48859.html","tags":["related","Mitigation","Third Party Advisory","web","report"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-48859","tags":["related","Mitigation","Third Party Advisory","web","report"]},{"url":"https://www.erlang.org/doc/system/versions.html#order-of-versions","tags":["x_version-scheme","Product","web"]},{"url":"https://github.com/erlang/otp/commit/c342092ef4b369bb409d5b71ac8fd83bab74aedf","tags":["patch","Patch","fix"]},{"url":"https://github.com","tags":["web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48859.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48859","tags":["advisory"]},{"url":"https://github.com/erlang/otp","tags":["package"]},{"url":"https://ubuntu.com/security/CVE-2026-48859","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-48859","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-48859","title":"SSH server timing side-channel in ssh_auth:check_password/3 allows unauthenticated username enumeration","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.\n\nWhen 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.\n\nThe user_passwords and password options are documented as intended for test purposes; the recommended alternative is pwdfun, which is not affected by this vulnerability.\n\nThis vulnerability is associated with program files lib/ssh/src/ssh_auth.erl and lib/ssh/src/ssh_options.erl.\n\nThis issue affects OTP from OTP 29.0 before OTP 29.0.2, corresponding to ssh from 6.0 before 6.0.1.","status":"published","published":"2026-06-10T14:35:43.553Z","modified":"2026-09-08T01:05:48.773Z","cvss":[{"version":"4.0","score":6.3,"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","level":"medium","assessor":"cna"}],"cwes":["CWE-208"],"updated_at":"2026-11-02T13:50:49.872037Z"}],"euvd":[{"id":"EUVD-2026-36054","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.\n\nWhen 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.\n\nThe user_passwords and password options are documented as intended for test purposes; the recommended alternative is pwdfun, which is not affected by this vulnerability.\n\nThis vulnerability is associated with program files lib/ssh/src/ssh_auth.erl and lib/ssh/src/ssh_options.erl.\n\nThis issue affects OTP from OTP 29.0 before OTP 29.0.2, corresponding to ssh from 6.0 before 6.0.1.","status":"published","published":"2026-06-10T14:35:43Z","modified":"2026-09-08T01:05:48Z","cvss":[{"version":"4.0","score":6.3,"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","level":"medium"}],"updated_at":"2026-11-02T17:28:30.317832Z"}],"nvd":[{"id":"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.\n\nWhen 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.\n\nThe user_passwords and password options are documented as intended for test purposes; the recommended alternative is pwdfun, which is not affected by this vulnerability.\n\nThis vulnerability is associated with program files lib/ssh/src/ssh_auth.erl and lib/ssh/src/ssh_options.erl.\n\nThis issue affects OTP from OTP 29.0 before OTP 29.0.2, corresponding to ssh from 6.0 before 6.0.1.","status":"published","published":"2026-06-10T16:17:12.373Z","modified":"2026-10-26T11:10:00.157Z","cvss":[{"version":"4.0","score":6.3,"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium","assessor":"secondary"},{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-208"],"updated_at":"2026-11-02T14:12:23.485267Z"}],"osv":[{"id":"CVE-2026-48859","title":"SSH server timing side-channel in ssh_auth:check_password/3 allows unauthenticated username enumeration","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.\n\nWhen 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.\n\nThe user_passwords and password options are documented as intended for test purposes; the recommended alternative is pwdfun, which is not affected by this vulnerability.\n\nThis vulnerability is associated with program files lib/ssh/src/ssh_auth.erl and lib/ssh/src/ssh_options.erl.\n\nThis issue affects OTP from OTP 29.0 before OTP 29.0.2, corresponding to ssh from 6.0 before 6.0.1.","status":"published","published":"2026-06-10T14:35:43.553Z","modified":"2026-10-28T02:31:12.536893631Z","cvss":[{"version":"4.0","score":6.3,"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","level":"medium"}],"cwes":["CWE-208"],"updated_at":"2026-11-02T15:45:07.060148Z"},{"id":"EEF-CVE-2026-48859","title":"SSH server timing side-channel in ssh_auth:check_password/3 allows unauthenticated username enumeration","description":"## Summary\n\nObservable Timing Discrepancy vulnerability in Erlang/OTP ssh (ssh_auth, ssh_options modules) allows unauthenticated remote username enumeration via timing side-channel in password authentication.\n\nWhen 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.\n\nThe `user_passwords` and `password` options are documented as intended for test purposes; the recommended alternative is `pwdfun`, which is not affected by this vulnerability.\n\nThis vulnerability is associated with program files `lib/ssh/src/ssh_auth.erl` and `lib/ssh/src/ssh_options.erl`.\n\nThis issue affects OTP from OTP 29.0 before OTP 29.0.2, corresponding to ssh from 6.0 before 6.0.1.\n\n## Workarounds\n\n* Use the `pwdfun` option instead of `user_passwords` for password authentication. The `pwdfun` callback gives full control over timing behavior and is not affected by this vulnerability. Implementations should take care to execute in approximately constant time regardless of username validity.\n* Restrict SSH port access to trusted networks only via firewall rules, reducing the set of potential attackers who can perform timing measurements.\n\n## Configurations\n\nThe SSH daemon must be configured with the `user_passwords` or `password` option for password authentication. Systems using the `pwdfun` option instead are not affected.","status":"published","published":"2026-06-10T14:35:43.553Z","modified":"2026-09-08T01:15:05.84316555Z","cvss":[{"version":"4.0","score":6.3,"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","level":"medium"}],"cwes":["CWE-208"],"updated_at":"2026-11-02T15:46:33.520522Z"},{"id":"UBUNTU-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.","status":"published","published":"2026-06-10T16:17:00Z","modified":"2026-10-06T23:31:18.771716343Z","cvss":[{"version":"4.0","score":6.3,"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","level":"medium"},{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"updated_at":"2026-11-02T16:56:33.391918Z"}]}}