CVE-2026-55205 Hermes WebUI < 0.51.468 - Resource Exhaustion via Unauthenticated OAuth Flow Endpoint
Unauthenticated attackers can exhaust server memory and threads via the OAuth onboarding endpoint, causing denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-55205?
CVE-2026-55205 is a medium-severity denial of service vulnerability in nesquena hermes-webui, published on 18 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-770
Which versions are affected by CVE-2026-55205?
How do I fix CVE-2026-55205?
No fix has been published for CVE-2026-55205 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-55205 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55205 exists.
Sources
Also known as GHSA-hq7f-wv7c-w9mp.