Hermes WebUI before version 0.51.358 contains an improper access control vulnerability that allows unauthenticated remote attackers to hijack initial setup by submitting the _set_password parameter to the settings API endpoint without any network origin restriction. Attackers on any reachable network can send a POST request to the settings endpoint during the first-run setup window to persist an arbitrary password hash, obtain a valid session cookie, and lock out the legitimate operator from their own instance.
https://www.vulncheck.com/advisories/hermes-webui-unauthenticated-password-takeover-via-api-settings
https://github.com/nesquena/hermes-webui/releases/tag/v0.51.358
https://github.com/nesquena/hermes-webui/pull/3973
https://github.com/nesquena/hermes-webui/pull/3964
https://github.com/nesquena/hermes-webui/commit/1126e541325d401538f6a272a9c024c37d47ae08
Published: 2026-06-11
Updated: 2026-06-11
Base Score: 9.7
Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:P
Severity: High
Base Score: 9.4
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Severity: Critical
Base Score: 9.2
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
Severity: Critical
EPSS: 0.00072