How severe is CVE-2026-66065?

No CVSS score has been assigned to CVE-2026-66065 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-66065?

CVE-2026-66065 affects the following packages: ouroboros-ai (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-66065?

Update ouroboros-ai to 0.42.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-66065 is resolved across your whole dependency graph.

How do I detect CVE-2026-66065 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ouroboros-ai, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-66065 if there is no patch (or I can't update yet)?

Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Is CVE-2026-66065 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-66065 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-66065?

CVE-2026-66065 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 14th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-66065?

CVE-2026-66065 is classified as CWE-15 (CWE-15), Code Injection (CWE-94). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-66065 published, and has it been updated?

CVE-2026-66065 was published on August 3, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-66065 — ouroboros-ai

CVE-2026-66065 is a CWE-15 vulnerability in ouroboros-ai. A fix is available for ouroboros-ai — see the affected versions and patch details below.

Ouroboros: Untrusted project .env can still reach RCE via omitted execution-routing keys (Incomplete fix of CVE-2026-47211)

Also known asGHSA-jv2h-4p9v-wf5w

Published

Aug 3, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-66065.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs14th percentile — riskier than 14% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍ouroboros-ai

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

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).

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`ouroboros-ai`	all versions	0.42.1`pip install --upgrade 'ouroboros-ai==0.42.1'`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ouroboros-ai, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update ouroboros-ai to 0.42.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-66065 is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Frequently Asked Questions

### 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` redir

O3 Security · Impact-Aware SCA

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