# CVE-2026-55197: Hermes WebUI < 0.51.443 - Broken Access Control in /api/session Endpoint

> Authenticated users can bypass profile boundaries to read other users' session transcripts and metadata via the /api/session endpoint.

- **Severity:** High 7.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 17 Jun 2026
- **Updated:** 17 Sep 2026
- **Also known as:** GHSA-5wqv-fhmr-pjgh

## What is CVE-2026-55197?

CVE-2026-55197 is a high-severity missing authorization vulnerability in nesquena hermes-webui, published on 17 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Hermes WebUI before 0.51.443 contains a broken access control vulnerability in the /api/session endpoint that allows authenticated users to disclose cross-profile session transcripts. Attackers can bypass profile boundary checks by directly querying session IDs belonging to other profiles via GET /api/session?session_id=<foreign_id>&messages=1 to retrieve unauthorized conversation transcripts and metadata.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-55197?


## How do I fix CVE-2026-55197?

No fix has been published for CVE-2026-55197 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-55197 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55197 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55197 and fix it if it is affected.

What it is: CVE-2026-55197 is a high-severity missing authorization vulnerability in nesquena hermes-webui, published on 17 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55197 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-2026-55197/ (Markdown: https://insights.sbomify.com/CVE-2026-55197/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55197
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55197
- OSV: https://osv.dev/vulnerability/CVE-2026-55197

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-55197/
Summaries are generated and may contain mistakes; the official description above is the record.