# CVE-2026-84288: NousResearch hermes-agent ACP Prompt Workflow session.py HermesACPAgent.prompt denial of service

> Remote attackers can cause denial of service in NousResearch hermes-agent via the ACP Prompt Workflow session handler.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P`)
- **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:** 1 Sep 2026
- **Updated:** 2 Sep 2026
- **Also known as:** GHSA-4pg4-vjj9-4j5w

## What is CVE-2026-84288?

CVE-2026-84288 is a medium-severity denial of service vulnerability in NousResearch hermes-agent, published on 1 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A vulnerability has been found in NousResearch hermes-agent up to 0.18.2. This affects the function HermesACPAgent.prompt of the file acp_adapter/session.py of the component ACP Prompt Workflow. Such manipulation leads to denial of service. The attack may be performed from remote. The exploit has been disclosed to the public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.

Weakness: CWE-404 (Improper Resource Shutdown or Release)

## Which versions are affected by CVE-2026-84288?


## How do I fix CVE-2026-84288?

No fix has been published for CVE-2026-84288 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-84288 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-84288 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-84288 and fix it if it is affected.

What it is: CVE-2026-84288 is a medium-severity denial of service vulnerability in NousResearch hermes-agent, published on 1 Sep 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-2026-84288 exists.

Affected product: NousResearch hermes-agent. 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-2026-84288/ (Markdown: https://insights.sbomify.com/CVE-2026-84288/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-84288
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-84288
- OSV: https://osv.dev/vulnerability/CVE-2026-84288

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-84288/
Summaries are generated and may contain mistakes; the official description above is the record.