diff --git a/scripts/release.py b/scripts/release.py
index 3ce210ade921..ef343c30ae3c 100755
--- a/scripts/release.py
+++ b/scripts/release.py
@@ -47,6 +47,7 @@ ACP_REGISTRY_MANIFEST = REPO_ROOT / "acp_registry" / "agent.json"
 AUTHOR_MAP = {
     "der@konsi.org": "konsisumer",  # PR #19608 salvage (read-modify-write merge in write_credential_pool to preserve concurrently-added credentials; #19566)
     "linyubin@users.noreply.github.com": "linyubin",  # PR #50228 salvage (eager fallback on persistent transport timeout/overloaded; #22277)
+    "65363919+coygeek@users.noreply.github.com": "coygeek",  # PR #37951 salvage (fail closed when provider env blocklist import fails; #37950)
     "5261694+djstunami@users.noreply.github.com": "djstunami",  # PR #5316 salvage / co-author (suppress transient check_fn flakes so subagents keep file/terminal tools; #21658 / #5304)
     "jmmaloney4@gmail.com": "jmmaloney4",  # PR #25206 salvage (re-select credential pool on primary runtime restore; #25205)
     "dale@dalenguyen.me": "dalenguyen",  # PR #53678 salvage (strip VIRTUAL_ENV/CONDA_PREFIX from terminal subprocess env; #23473)
diff --git a/tests/tools/test_env_passthrough.py b/tests/tools/test_env_passthrough.py
index 974911e588d3..a9d706636cbb 100644
--- a/tests/tools/test_env_passthrough.py
+++ b/tests/tools/test_env_passthrough.py
@@ -228,3 +228,52 @@ class TestTerminalIntegration:
         # Arbitrary skill-specific var
         register_env_passthrough(["MY_SKILL_CUSTOM_CONFIG"])
         assert is_env_passthrough("MY_SKILL_CUSTOM_CONFIG")
+
+    def test_provider_blocklist_import_failure_fails_closed(self, monkeypatch):
+        """If the dynamic provider blocklist can't be imported, provider
+        credentials must be treated as protected and refused passthrough —
+        otherwise a skill could tunnel a Hermes credential into the
+        execute_code child (regression for #37950 / GHSA-rhgp-j443-p4rf).
+
+        Verifies the full path: _is_hermes_provider_credential returns True,
+        register_env_passthrough refuses the var, and _scrub_child_env keeps
+        it out of the child env. A non-Hermes key is also rejected here (the
+        fallback is conservative: when we can't tell, we fail closed), which
+        is the safe direction.
+        """
+        import builtins
+
+        from tools.code_execution_tool import _scrub_child_env
+
+        real_import = builtins.__import__
+
+        def fail_local_import(name, *args, **kwargs):
+            if name == "tools.environments.local":
+                raise ImportError("synthetic blocklist import failure")
+            return real_import(name, *args, **kwargs)
+
+        monkeypatch.setattr(builtins, "__import__", fail_local_import)
+
+        # Every name is now treated as a protected provider credential.
+        assert _ep_mod._is_hermes_provider_credential("OPENAI_API_KEY")
+        assert _ep_mod._is_hermes_provider_credential("ANTHROPIC_API_KEY")
+        assert _ep_mod._is_hermes_provider_credential("GH_TOKEN")
+
+        # Registration is refused while the blocklist is unavailable.
+        register_env_passthrough(["OPENAI_API_KEY", "ANTHROPIC_API_KEY"])
+        assert not is_env_passthrough("OPENAI_API_KEY")
+        assert not is_env_passthrough("ANTHROPIC_API_KEY")
+
+        # And the credential never reaches the execute_code child.
+        child_env = _scrub_child_env(
+            {
+                "OPENAI_API_KEY": "synthetic-secret",
+                "ANTHROPIC_API_KEY": "synthetic-secret",
+                "PATH": "/usr/bin",
+            },
+            is_passthrough=is_env_passthrough,
+            is_windows=False,
+        )
+        assert "OPENAI_API_KEY" not in child_env
+        assert "ANTHROPIC_API_KEY" not in child_env
+        assert child_env["PATH"] == "/usr/bin"
diff --git a/tools/env_passthrough.py b/tools/env_passthrough.py
index 5efee177d003..51bff8defdf7 100644
--- a/tools/env_passthrough.py
+++ b/tools/env_passthrough.py
@@ -59,11 +59,22 @@ def _is_hermes_provider_credential(name: str) -> bool:
     Non-Hermes API keys (TENOR_API_KEY, NOTION_TOKEN, etc.) are NOT
     in the blocklist and remain legitimately registerable — skills that
     wrap third-party APIs still work.
+
+    Fail closed: if the authoritative blocklist cannot be imported (partial
+    install, import-time error, etc.) we treat the name as a protected
+    provider credential and refuse passthrough, rather than fall open and
+    let a skill tunnel a Hermes credential into the execute_code child.
     """
     try:
         from tools.environments.local import _HERMES_PROVIDER_ENV_BLOCKLIST
-    except Exception:
-        return False
+    except Exception as e:
+        logger.warning(
+            "env passthrough: provider credential blocklist import failed; "
+            "failing closed and refusing passthrough registration for %r: %s",
+            name,
+            e,
+        )
+        return True
     return name in _HERMES_PROVIDER_ENV_BLOCKLIST