CVE-2026-84289Public exploitNetwork attack vectorHinoki check available

API service interruption via unbounded MCP metadata

Published Sep 1, 2026 · Updated Sep 2, 2026

Resource exhaustion in Nous Research Hermes Agent 0.18.0 through 0.18.2 allows remote authenticated users to interrupt API service. The MCP Tool's list_tools path retains the full tool list and registers unbounded descriptions and schemas without count, size, or depth limits. Exploitation requires an API key, an enabled API server, and a configured MCP server able to return oversized metadata or results, which can exhaust shared chat concurrency and produce HTTP 429 responses.

CVSS severityUnavailable
Unscored
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Resource exhaustion in Nous Research Hermes Agent 0.18.0 through 0.18.2 allows remote authenticated users to interrupt API service. The MCP Tool's list_tools path retains the full tool list and registers unbounded descriptions and schemas without count, size, or depth limits. Exploitation requires an API key, an enabled API server, and a configured MCP server able to return oversized metadata or results, which can exhaust shared chat concurrency and produce HTTP 429 responses.

The record

CVE
CVE-2026-84289
Published
Sep 1, 2026
Updated
Sep 2, 2026
Vendor
Nous Research
Product
Hermes Agent
Classifications
CWE-789, CWE-400, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.18.0
  2. Affected versionversion=0.18.1
  3. Affected versionversion=0.18.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nous Research · Hermes Agentversion=0.18.0; version=0.18.1; version=0.18.2

Published CVSS scores

4.3VulDB CNACVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:X/RC:R
5.3VulDB CNACVSS: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
4.3VulDB CNACVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:X/RC:R
4.0VulDB CNAAV:N/AC:L/Au:S/C:N/I:N/A:P/E:POC/RL:ND/RC:UR

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-789Uncontrolled Memory Allocation
CWE-400Resource Consumption
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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