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.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
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
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.
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-2026-84288 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-84288 exists.
Sources
Also known as GHSA-4pg4-vjj9-4j5w.