What’s Vulnerable › Vulnerabilities

CVE-2026-55205: Hermes WebUI < 0.51.468 - Resource Exhaustion via Unauthenticated OAuth Flow Endpoint

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-18 · updated 2026-10-26
• Weakness: CWE-770

Description

Hermes WebUI before 0.51.468 contains a resource exhaustion vulnerability in the unauthenticated POST /api/onboarding/oauth/start endpoint that allows unbounded accumulation of in-memory flow state and daemon threads. Attackers can send repeated or concurrent requests to exhaust server memory and thread resources, potentially triggering repeated outbound device-code requests to upstream OAuth providers.

Affected products

• nesquena hermes-webui: before 0.51.468 — fixed in 0.51.468

How to fix

Upgrade to a fixed version: nesquena hermes-webui 0.51.468. Check the vendor advisory for mitigations.

References

• https://github.com/nesquena/hermes-webui/commit/ce272d9cd5f8e5a4521278f56eb5388010901646
• https://github.com/nesquena/hermes-webui/pull/3970
• https://github.com/nesquena/hermes-webui/pull/4338
• https://github.com/nesquena/hermes-webui/releases/tag/v0.51.468
• https://www.vulncheck.com/advisories/hermes-webui-resource-exhaustion-via-unauthenticated-oauth-flow-endpoint
• https://github.com/nesquena/hermes-webui/pull/3970

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