CVE-2026-9366: Hermes agent Hermes-agent Has An Injection Issue Vulnerability

MODERATE
Advisory Identifier: GHSA-pgp4-xr4j-h5cg
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CVSS 7.3
CWE-74
Published
Advisory Summary

CVE-2026-9366 is a MODERATE (CVSS 7.3) hermes-agent has an injection issue vulnerability (CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')) affecting Hermes agent libraries in the PyPI ecosystem. The issue involves hermes-agent has an injection issue. Remediation is available by upgrading affected packages to version 0.15.0.

CVE-2026-9366 at a Glance

CVE Identifier CVE-2026-9366
GHSA Identifier GHSA-pgp4-xr4j-h5cg
Severity MODERATE
CVSS v3.1 Base Score 7.3
CWE Classification CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Affected Product Hermes agent
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2026-9366

To remediate this vulnerability, upgrade all affected Hermes agent dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

hermes-agent fixed: 0.15.0 
pip install hermes-agent>=0.15.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show hermes-agent

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-9366, inspect your installed packages using pip:

pip show hermes-agent

Analyze the terminal output to locate any version of Hermes agent in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.15.0), your application is affected.

Note: The pip show hermes-agent command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection'), where the product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. In Hermes agent, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

A vulnerability was found in NousResearch hermes-agent 2026.4.23. The impacted element is the function _scan_context_content of the file agent/prompt_builder.py. The manipulation results in injection. The attack may be performed from remote. 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.

CVE-2026-9366 Affected Hermes agent Versions

1 component(s)
Fixed Versions:
0.15.0
Product / Package Ecosystem Affected Versions Fixed Version
hermes-agent
pypi/hermes-agent
PyPI
< 0.15.0
0.15.0

References

vuldb.com/vuln/365329/cti WEB
https://vuldb.com/vuln/365329/cti
NVD — CVE-2026-9366 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-9366
Security Fix Commit FIX COMMIT
https://github.com/NousResearch/hermes-agent/commit/0dee92df22bdc0cfbcad90ca954aa14916f018de
Hermes agent Source Repository REPOSITORY
https://gist.github.com/YLChen-007/581fd92de5548fbaacb2092e848a75cc
Hermes agent Source Repository REPOSITORY
https://github.com/NousResearch/hermes-agent
vuldb.com/submit/812227 WEB
https://vuldb.com/submit/812227
vuldb.com/vuln/365329 WEB
https://vuldb.com/vuln/365329

Frequently Asked Questions

What is CVE-2026-9366?
CVE-2026-9366 is a security vulnerability in Hermes agent involving hermes-agent has an Injection issue under CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection').
Which Hermes agent versions are affected?
Affected versions include releases prior to 0.15.0 across affected packages: hermes-agent.
What version fixes CVE-2026-9366?
Upgrading to 0.15.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is hermes-agent affected?
Yes, hermes-agent is affected in releases prior to 0.15.0. Upgrade your dependency to 0.15.0 or later.
What is the CVSS score of CVE-2026-9366?
CVE-2026-9366 has a CVSS v3.1 base score of 7.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L.
What CWE is associated with CVE-2026-9366?
CVE-2026-9366 is classified under CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') (The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.).
How can I check PyPI dependencies for CVE-2026-9366?
Run the dependency tree command: 'pip show hermes-agent'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-pgp4-xr4j-h5cg",
  "modified" : "2026-06-30T15:34:03Z",
  "published" : "2026-05-26T13:30:31Z",
  "aliases" : [ "CVE-2026-9366" ],
  "summary" : "hermes-agent has an Injection issue",
  "details" : "A vulnerability was found in NousResearch hermes-agent 2026.4.23. The impacted element is the function _scan_context_content of the file agent/prompt_builder.py. The manipulation results in injection. The attack may be performed from remote. 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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P"
  } ],
  "affected" : [ {
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    },
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      "type" : "ECOSYSTEM",
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      } ]
    } ]
  } ],
  "references" : [ {
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  }, {
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    "url" : "https://gist.github.com/YLChen-007/581fd92de5548fbaacb2092e848a75cc"
  }, {
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  }, {
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  }, {
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    "url" : "https://vuldb.com/vuln/365329"
  }, {
    "type" : "WEB",
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  } ],
  "database_specific" : {
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    "github_reviewed_at" : "2026-06-30T15:34:03Z",
    "nvd_published_at" : "2026-05-24T09:16:32Z"
  }
}