Vulnerability in Nousresearch Hermes-Agent
CVE-2026-82021
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.3 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.003 (25.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 25th percentile — 25.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
Weakness classification (CWE)
References
- github.com/NousResearch/hermes-agent/releases/tag/v2026.7.20 (release-notes)
- github.com/NousResearch/hermes-agent/pull/64463 (issue-tracking, patch)
- github.com/NousResearch/hermes-agent/commit/9df5f879b4a5925c0f8f947e7e16ed8e845… (patch)
- www.vulncheck.com/advisories/hermes-agent-mcp-catalog-supply-chain-rce-via-muta… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-82021?
- CVE-2026-82021 is a high-severity vulnerability in Nousresearch Hermes-Agent, classified under Download of Code Without Integrity Check. CVSS score: 8.3/10. Published 2026-08-28.
- How severe is CVE-2026-82021?
- High severity. CVSS v3 base score is 8.3 out of 10.