# 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.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 18 Jun 2026
- **Updated:** 17 Sep 2026
- **Also known as:** GHSA-hq7f-wv7c-w9mp

## 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 (Allocation of Resources Without Limits or Throttling)

## 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.

## Is CVE-2026-55205 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55205 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55205 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55205 exists.

Affected product: nesquena hermes-webui. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-55205/ (Markdown: https://insights.sbomify.com/CVE-2026-55205/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55205
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55205
- OSV: https://osv.dev/vulnerability/CVE-2026-55205

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55205/
Summaries are generated and may contain mistakes; the official description above is the record.