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Hermes WebUI CVE-2026-58122

| EUVDEUVD-2026-42726 CRITICAL
Use of Less Trusted Source (CWE-348)
2026-07-09 VulnCheck GHSA-rfj2-6v8r-3w64
Authentication Bypass SSRF Hermes Webui
9.3
CVSS 4.0 · Vendor: VulnCheck
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Severity by source

Vendor (VulnCheck) PRIMARY
9.3 CRITICAL
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/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
vuln.today AI
9.1 CRITICAL

Remote, unauthenticated, low-complexity header spoof (AV:N/AC:L/PR:N/UI:N) yielding SSRF/credential disclosure (C:H) and config/key overwrite (I:H) with no availability loss (A:N).

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/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
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

1
Analysis Generated
Jul 09, 2026 - 22:09 vuln.today

DescriptionCVE.org

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.

AnalysisAI

Authentication bypass in Hermes WebUI before 0.51.307 lets unauthenticated remote attackers reach onboarding endpoints that are supposed to be restricted to loopback traffic by spoofing an X-Forwarded-For header with a 127.0.0.1 value. Once past the origin check, an attacker can pivot to server-side request forgery against internal services and cloud metadata endpoints, overwrite LLM provider configuration and API keys, or start an OAuth device-code flow to mint persistent tokens saved in auth.json. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Locate exposed Hermes WebUI
Delivery
Send request with spoofed X-Forwarded-For: 127.0.0.1
Exploit
Bypass local-origin onboarding check
Execution
SSRF to cloud metadata / overwrite API keys
Persist
Trigger OAuth device-code flow
Impact
Persist token in auth.json
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Vulnerability AssessmentAI

Exploitation Exploitation requires that the Hermes WebUI instance (version below 0.51.307) be network-reachable by the attacker and that the onboarding endpoints rely on the X-Forwarded-For header for their local-origin restriction, which is the default vulnerable behavior. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The signals are consistent and point to a genuine priority. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker discovers an internet-reachable Hermes WebUI instance and sends a crafted HTTP request to an onboarding endpoint with the header X-Forwarded-For: 127.0.0.1, defeating the local-origin restriction. They then abuse the SSRF sink to query the cloud metadata endpoint for IAM credentials, overwrite the configured LLM provider API keys with their own, and trigger an OAuth device-code flow to persist an access token in auth.json. …
Remediation Vendor-released patch: upgrade to Hermes WebUI v0.51.307 or later, which is the primary and complete fix (release: https://github.com/nesquena/hermes-webui/releases/tag/v0.51.307; fix PR https://github.com/nesquena/hermes-webui/pull/3758; patch commit https://github.com/nesquena/hermes-webui/commit/70596e6993be0d4cee083c1c1a86f5e7ad5d57b7). … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours: Inventory all Hermes WebUI deployments and determine current versions; immediately restrict network access to onboarding endpoints if running pre-0.51.307 instances. …

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CVE-2026-58122 vulnerability details – vuln.today
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