{"id":"CVE-2026-66065","aliases":["GHSA-jv2h-4p9v-wf5w"],"url":"https://o3.security/vulnerability/CVE-2026-66065","summary":"Ouroboros: Untrusted project .env can still reach RCE via omitted execution-routing keys (Incomplete fix of CVE-2026-47211)","details":"### Impact\nThe CVE-2026-47211 fix (0.39.0) added `_UNTRUSTED_ENV_DENYLIST` to stop an untrusted project-directory `.env` from redirecting execution. The denylist was incomplete — 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, no review step):\n\n- **Backend config-home roots** `CODEX_HOME`, `OPENCODE_CONFIG`, `OPENCODE_CONFIG_DIR`, `XDG_CONFIG_HOME`: a spawned vendor CLI resolves its config from these. `CODEX_HOME=./.evil` + committed `./.evil/config.toml` redirects the nested Codex agent to attacker config — `mcp_servers.<name>.command/args` (RCE) and `approval_policy=\"never\"` / `sandbox_mode=\"danger-full-access\"` (silent removal of the human approval gate). (reported by matte1782)\n- **MCP bridge / plugin execution roster** `OUROBOROS_MCP_CONFIG` (the YAML's server `command`/`args` are spawned via stdio_client — RCE), `OUROBOROS_PLUGIN_LOCKFILE`, `OUROBOROS_PLUGIN_TRUST_ROOT` (redirect the installed-plugin roster / trust root so `ooo <name>` dispatches into attacker code). (reported by hackkim)\n- **SSRF guard toggle** `OUROBOROS_ALLOW_LOCAL_TRANSPORT` (re-enables loopback/private MCP transport targets).\n- **Instruction / capability roots** `OUROBOROS_AGENTS_DIR`, `COPILOT_CUSTOM_INSTRUCTIONS_DIRS` (replace spawned sub-agent role prompts), `OUROBOROS_RUNTIME_PROFILE` (backend selector), `OUROBOROS_TOOL_CAPABILITIES` (override YAML can lower a tool's `approval_class`, weakening the approval gate).\n\nAdditionally, the MCP bridge auto-loaded `./.ouroboros/mcp_servers.yaml` from the working directory (`create_bridge_from_env(cwd=Path.cwd())`), so running `ooo` inside a malicious repo spawned the committed roster's `command` — RCE with no `.env` at all. (cwd-branch noted by hackkim)\n\n### Patches\nFixed in 0.42.1. All listed keys were added to `_UNTRUSTED_ENV_DENYLIST`; the cwd auto-discovery branch was removed (only the explicit `OUROBOROS_MCP_CONFIG` env var and `~/.ouroboros/mcp_servers.yaml` remain, both trusted). The regression suite now derives from the source denylist to prevent future drift.\n\n### Workarounds\nDo not run Ouroboros from an untrusted/cloned repository directory; remove any project-directory `.env` and `./.ouroboros/mcp_servers.yaml` before running.\n\n### Credit\nReported privately via coordinated disclosure by matte1782 and hackkim (https://github.com/hackkim).","published":"2026-08-03T20:20:27.599Z","modified":"2026-10-21T02:58:59.474597637Z","cvss":null,"epss":{"score":0.00297,"percentile":0.22371,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"ouroboros-ai","fixedVersion":"0.42.1"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/Q00/ouroboros/releases/tag/v0.42.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66065.json"},{"type":"ADVISORY","url":"https://github.com/Q00/ouroboros/security/advisories/GHSA-jv2h-4p9v-wf5w"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66065"},{"type":"PACKAGE","url":"https://github.com/Q00/ouroboros"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:58:59.474597637Z"}}