Description
A vulnerability was found in NousResearch hermes-agent up to 0.18.2. This vulnerability affects the function list_tools of the file tools/mcp_tool.py of the component MCP Tool. Performing a manipulation results in uncontrolled memory allocation. It is possible to initiate the attack remotely. The exploit has been made public and could be used. The vendor was contacted early about this disclosure but did not respond in any way.
Published: 2026-09-01
Score: 5.3 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

The Hermes-agent MCP Tool contains a flaw in the list_tools function that allows an attacker to supply input that triggers uncontrolled memory allocation, potentially exhausting system resources and causing a denial of service. This results in degraded availability for any process relying on the agent and may impact overall system stability.

Affected Systems

The vulnerability affects all NousResearch Hermes-agent deployments on or before version 0.18.2. Any instance running a vulnerable version is subject to risk until an updated release is applied.

Risk and Exploitability

The CVSS score of 5.3 indicates moderate severity. The exploit is remote and publicly documented, and no EPSS data is available, but the lack of a KEV listing suggests a lower observed exploitation rate. An attacker can trigger the vulnerability by sending crafted requests to the MCP tool over the network, leading to resource exhaustion and service interruption.

Generated by OpenCVE AI on September 1, 2026 at 23:23 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Update Hermes-agent to a release newer than 0.18.2 once available from NousResearch.
  • Apply size limits or input validation to the list_tools parameters to prevent excessive memory allocation, mitigating the CWE-400 and CWE-789 weaknesses.
  • Temporarily disable or restrict remote access to the MCP tool if it is not required for operations, reducing the attack surface.

Generated by OpenCVE AI on September 1, 2026 at 23:23 UTC.

Tracking

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Advisories

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History

Tue, 01 Sep 2026 22:00:00 +0000

Type Values Removed Values Added
Description A vulnerability was found in NousResearch hermes-agent up to 0.18.2. This vulnerability affects the function list_tools of the file tools/mcp_tool.py of the component MCP Tool. Performing a manipulation results in uncontrolled memory allocation. It is possible to initiate the attack remotely. The exploit has been made public and could be used. The vendor was contacted early about this disclosure but did not respond in any way.
Title NousResearch hermes-agent MCP Tool mcp_tool.py list_tools memory allocation
First Time appeared Nousresearch
Nousresearch hermes-agent
Weaknesses CWE-400
CWE-789
CPEs cpe:2.3:a:nousresearch:hermes-agent:*:*:*:*:*:*:*:*
Vendors & Products Nousresearch
Nousresearch hermes-agent
References
Metrics cvssV2_0

{'score': 4, 'vector': 'AV:N/AC:L/Au:S/C:N/I:N/A:P/E:POC/RL:ND/RC:UR'}

cvssV3_0

{'score': 4.3, 'vector': 'CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:X/RC:R'}

cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:X/RC:R'}

cvssV4_0

{'score': 5.3, 'vector': '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'}

Subscriptions

Nousresearch Hermes-agent
cve-icon MITRE

Status: PUBLISHED

Assigner: VulDB

Published:

Updated: 2026-09-01T21:45:09.843Z

Reserved: 2026-09-01T15:48:59.951Z

Link: CVE-2026-84289

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-01T22:17:18.813

Modified: 2026-09-01T22:17:18.813

Link: CVE-2026-84289

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-01T23:30:05Z

Weaknesses
  • CWE-400

    Uncontrolled Resource Consumption

  • CWE-789

    Memory Allocation with Excessive Size Value