# CVE-2026-84288: NousResearch hermes-agent denial of service in ACP Prompt Workflow

Source: https://junglewise.ai/threats/cve-2026-84288-nousresearch-hermes-agent-denial-of-service-in-acp-prompt  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-01. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-84288 · Severity: medium · CVSS 4.3 · Published 2026-09-01

NousResearch hermes-agent is an AI agent framework used for building autonomous systems. A denial-of-service vulnerability in the ACP (Agent Communication Protocol) Prompt Workflow component allows remote attackers to cause service unavailability, disrupting the availability of applications built with this library.

Technologies: [NousResearch Hermes Agent](https://junglewise.ai/threats/technologies/hermes-agent). Vendors: [NousResearch](https://junglewise.ai/threats/vendors/nousresearch).

## Quick answers

**Is CVE-2026-84288 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-84288 being exploited in the wild.

**How severe is CVE-2026-84288?** Medium severity, with a CVSS score of 4.3, published 1 September 2026.

**Which products and versions are affected?** NousResearch Hermes Agent up to 0.18.2.

**Is there a fix for CVE-2026-84288?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-84288 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-84288?** Check whether you run NousResearch Hermes Agent at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A denial-of-service vulnerability exists in the HermesACPAgent.prompt function within acp_adapter/session.py of the ACP Prompt Workflow component. The vulnerability allows remote attackers to trigger a denial-of-service condition through improper handling of queued prompts. No authentication is required, and the attack is network-accessible. The vulnerability has been publicly disclosed with proof-of-concept code available, though the vendor did not respond to early notification attempts. Patches or vendor updates have not been confirmed.

## Affected products

- NousResearch hermes-agent up to 0.18.2

## Timeline

- 2026-09-01: disclosed: Public disclosure with proof-of-concept code

## References

- [https://github.com/hackerguopeng/cve/tree/main/Hermes_ACP_Queued_Prompt_DoS_Report](https://github.com/hackerguopeng/cve/tree/main/Hermes_ACP_Queued_Prompt_DoS_Report)
- [https://vuldb.com/cve/CVE-2026-84288](https://vuldb.com/cve/CVE-2026-84288)

## Related threats

- [NousResearch hermes-agent resource exhaustion in resourceBufferFromUrl](https://junglewise.ai/threats/cve-2026-85107-nousresearch-hermes-agent-resource-exhaustion-in)
- [NousResearch hermes-agent server-side request forgery in Link Title Fetch](https://junglewise.ai/threats/cve-2026-85106-nousresearch-hermes-agent-server-side-request-forgery-in-link)
- [NousResearch hermes-agent authorization bypass in Session Management](https://junglewise.ai/threats/cve-2026-85105-nousresearch-hermes-agent-authorization-bypass-in-session)
- [NousResearch hermes-agent denial of service in MCP Tool](https://junglewise.ai/threats/cve-2026-84289-nousresearch-hermes-agent-denial-of-service-in-mcp-tool)
- [NousResearch hermes-agent denial of service in session chat](https://junglewise.ai/threats/cve-2026-84287-nousresearch-hermes-agent-denial-of-service-in-session-chat)