CVE-2026-82021 Hermes Agent 0.18.2 < 0.19.0 MCP Catalog Supply Chain RCE via Mutable Branch Reference
Remote attackers can execute arbitrary code on hosts installing the Hermes Agent MCP catalog by compromising an upstream repository referenced via a mutable branch.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-82021?
CVE-2026-82021 is a critical vulnerability in NousResearch hermes-agent, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-494
Which versions are affected by CVE-2026-82021?
How do I fix CVE-2026-82021?
No fix has been published for CVE-2026-82021 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-82021 being exploited?
There is no known exploitation of CVE-2026-82021 in the wild and no public exploit code.
Sources
Also known as GHSA-w9gw-vgmg-q67h.