Vulnerability · Published Jul 9, 2026 · Assigned by VulnCheck

CVE-2026-58122Hermes WebUI < 0.51.307 Authentication Bypass via X-Forwarded-For Header Spoofing

Critical 9.1

In plain English

A critical-severity security flaw in hermes-webui from nesquena. 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 31% of all known vulnerabilities).

Severity (CVSS 3.1)9.1Critical

Exploit odds (30 days)0.4%top 68.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Hermes WebUI before 0.51.307 contains an authentication bypass vulnerability that allows unauthenticated remote attackers to circumvent local-origin IP restrictions on onboarding endpoints by supplying a spoofed X-Forwarded-For header with a loopback address. Attackers can exploit this bypass to perform server-side request forgery against internal services including cloud metadata endpoints, overwrite LLM provider configuration and API keys with attacker-controlled values, or initiate OAuth device-code flows to obtain persistent access tokens stored in auth.json.

Affected products (as reported)

Vendor	Product	Versions
nesquena	hermes-webui	0 – before 0.51.307

Weakness: CWE-348 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References

Release Notes release-notes
Pull Request issue-tracking
Patch Commit patch
https://www.vulncheck.com/advisories/hermes-webui-authentication-bypass-via-x-forwarded-for-header-spoofing third-party-advisory