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GHSA-jv2h-4p9v-wf5w

HighCVSS 8.6 / 10
Published Jun 19, 2026·Last modified Jun 19, 2026
Affected Components(0)

No affected components available

Description

Impact

The 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):

  • 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)
  • 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)
  • SSRF guard toggle OUROBOROS_ALLOW_LOCAL_TRANSPORT (re-enables loopback/private MCP transport targets).
  • 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).

Additionally, 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)

Patches

Fixed 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.

Workarounds

Do not run Ouroboros from an untrusted/cloned repository directory; remove any project-directory .env and ./.ouroboros/mcp_servers.yaml before running.

Credit

Reported privately via coordinated disclosure by matte1782 and hackkim (https://github.com/hackkim).

Risk Scores
Base Score
8.6

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights.

Threat Intelligence
6.1

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
N/A

Probability that this vulnerability will be exploited in the wild within the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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High severity
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