CVE-2026-66065

What it is

Ouroboros is a local-first runtime for AI coding agents that records their actions and applies user-defined policies to constrain behavior. Versions prior to 0.42.1 have an incomplete denylist. Several execution-routing keys of the same RCE class were omitted, so a malicious cloned repo can still reach arbitrary command execution by shipping a .env (auto-loaded at import, with no review step). The CVE-2026-47211 fix added _UNTRUSTED_ENV_DENYLIST to stop an untrusted project-directory .env from redirecting execution, but it did not account for all keys. The backend config-home and MCP/plugin roots bypass the approval gate by pointing the nested agent, MCP servers, and plugin roster at attacker config. Other variables re-enable blocked local transports, replace sub-agent prompts, switch backends, and lower tool approval classes, further weakening the approval gate. This issue has been fixed in version 0.42.1.

At a glance

Exploitability

Can be exploited locally on the machine without logging in, but needs a user to act. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-08-03 21:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-23 21:10 UTC Last updatedMost recent change to the record

Details

Published

2026-08-03 21:16 UTC

Last modified

2026-10-23 21:10 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-15

Record status

Deferred

Attack profile CVSS 4.0 · 8.4

Attack vector

Local

Complexity

Low

Attack requirements

None

Privileges needed

None

User interaction

Active

Confidentiality

High

Integrity

High

Availability

High