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🛡️ CVE-2026-66065 — ouroboros-ai

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-15 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

ouroboros-ai: Incomplete fix of CVE-2026-47211: untrusted project .env can still reach RCE via omitted execution-routing keys

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).

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. A user must actively cooperate. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Attack requirements: None — no deployment-specific condition has to hold.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: Active — the victim has to cooperate with the attack.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-66065 is classified as CWE-15: External Control of System or Configuration Setting. One or more system settings or configuration elements can be externally controlled by a user.

Affected software

CVE-2026-66065 is recorded against 2 packages.

  • ouroboros-ai (fixed in 0.42.1)
  • unknown

Timeline and source

Published on 19 June 2026 and last revised on 4 August 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Web)
github.com (Package)

Other advisories for this package

ouroboros-ai has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-15: External Control of System or Configuration Setting) in other software:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CWE CWE-15
Public Exploit ✅ No
Source NVD
Published 2026-06-19
Updated 2026-08-20
Modified 2026-08-04
Fix URL N/A

Affected Packages

Software From version Fixed in
ouroboros-ai — 0.42.1
unknown — —

Similar Threats

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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