fix: validate aws region name

litellm/llms/bedrock/base_aws_llm.py

@@ -1,6 +1,7 @@
 import hashlib
 import json
 import os
+import re
 import urllib.parse
 from datetime import datetime
 from typing import (
@@ -37,6 +38,11 @@ else:
     AWSPreparedRequest = Any
 
 
+# Real AWS region names are lowercase letters, digits, and hyphens
+# (e.g. "us-east-1", "eu-west-2", "us-gov-west-1", "cn-north-1").
+_VALID_AWS_REGION_PATTERN = re.compile(r"\A[a-z0-9-]+\Z")
+
+
 class Boto3CredentialsInfo(BaseModel):
     credentials: Credentials
     aws_region_name: str
@@ -284,6 +290,9 @@ class BaseAWSLLM:
             if not region:  # Check if region is empty
                 return None
 
+            if not _VALID_AWS_REGION_PATTERN.match(region):
+                return None
+
             return region
         except Exception:
             # Catch any unexpected errors and return None
@@ -481,6 +490,7 @@ class BaseAWSLLM:
             str: The AWS region name
         """
         aws_region_name = optional_params.get("aws_region_name", None)
+        self._validate_aws_region_name(aws_region_name)
         ### SET REGION NAME ###
         if aws_region_name is None:
             # check model arn #
@@ -519,8 +529,25 @@ class BaseAWSLLM:
             except Exception:
                 aws_region_name = "us-west-2"
 
+        self._validate_aws_region_name(aws_region_name)
         return aws_region_name
 
+    @staticmethod
+    def _validate_aws_region_name(aws_region_name: Optional[str]) -> None:
+        """
+        Validate that an AWS region name conforms to the expected format
+        (lowercase alphanumerics and hyphens). Raises ValueError otherwise.
+        """
+        if aws_region_name is None:
+            return
+        if not isinstance(aws_region_name, str) or not _VALID_AWS_REGION_PATTERN.match(
+            aws_region_name
+        ):
+            raise ValueError(
+                f"Invalid AWS region format: {aws_region_name!r}. "
+                "Region names must contain only lowercase letters, digits, and hyphens."
+            )
+
     def get_aws_region_name_for_non_llm_api_calls(
         self,
         aws_region_name: Optional[str] = None,
@@ -532,6 +559,7 @@ class BaseAWSLLM:
 
         For non-llm api calls eg. Guardrails, Vector Stores we just need to check the dynamic param or env vars.
         """
+        self._validate_aws_region_name(aws_region_name)
         if aws_region_name is None:
             # check env #
             litellm_aws_region_name = get_secret("AWS_REGION_NAME", None)
@@ -549,6 +577,8 @@ class BaseAWSLLM:
 
             if aws_region_name is None:
                 aws_region_name = "us-west-2"
+
+        self._validate_aws_region_name(aws_region_name)
         return aws_region_name
 
     @staticmethod

tests/test_litellm/llms/bedrock/test_base_aws_llm.py

@@ -180,6 +180,140 @@ def test_get_aws_region_name_boto3_fallback():
             mock_boto3_session.assert_not_called()
 
 
+@pytest.mark.parametrize(
+    "bad_region",
+    [
+        "us-east-1@example.com/",
+        "us-east-1@example.com",
+        "us-east-1/path",
+        "us-east-1.example.com",
+        "us-east-1:8080",
+        "us-east-1#fragment",
+        "us-east-1?query=1",
+        "us-east-1\\path",
+        "US-EAST-1",  # uppercase not allowed
+        "us east 1",  # spaces not allowed
+        "",  # empty string not allowed
+        "us-east-1\n",  # trailing newline must not slip past $
+    ],
+)
+def test_get_aws_region_name_rejects_malformed_region(bad_region):
+    """
+    Region names are interpolated into endpoint URL templates, so any value
+    containing characters that would alter URL parsing must be rejected.
+    """
+    base_aws_llm = BaseAWSLLM()
+
+    with pytest.raises(ValueError, match="Invalid AWS region format"):
+        base_aws_llm._get_aws_region_name(
+            optional_params={"aws_region_name": bad_region}
+        )
+
+
+@pytest.mark.parametrize(
+    "valid_region",
+    [
+        "us-east-1",
+        "eu-west-2",
+        "ap-southeast-1",
+        "us-gov-west-1",
+        "cn-north-1",
+        "me-south-1",
+    ],
+)
+def test_get_aws_region_name_accepts_valid_regions(valid_region):
+    """Real AWS region formats must continue to work after the format guard."""
+    base_aws_llm = BaseAWSLLM()
+    result = base_aws_llm._get_aws_region_name(
+        optional_params={"aws_region_name": valid_region}
+    )
+    assert result == valid_region
+
+
+def test_get_aws_region_name_rejects_malformed_region_from_env():
+    """
+    A malformed AWS_REGION / AWS_REGION_NAME env value must also be rejected
+    before it can flow into a URL template.
+    """
+    base_aws_llm = BaseAWSLLM()
+
+    with patch("litellm.llms.bedrock.base_aws_llm.get_secret") as mock_get_secret:
+
+        def side_effect(key, default=None):
+            if key == "AWS_REGION_NAME":
+                return "us-east-1@example.com/"
+            return default
+
+        mock_get_secret.side_effect = side_effect
+
+        with pytest.raises(ValueError, match="Invalid AWS region format"):
+            base_aws_llm._get_aws_region_name(optional_params={})
+
+
+def test_get_aws_region_name_for_non_llm_api_calls_rejects_malformed_param():
+    """
+    The non-LLM helper (used by Guardrails, Vector Stores, etc.) must validate
+    a region passed in directly so it can't flow into a URL template.
+    """
+    base_aws_llm = BaseAWSLLM()
+
+    with pytest.raises(ValueError, match="Invalid AWS region format"):
+        base_aws_llm.get_aws_region_name_for_non_llm_api_calls(
+            aws_region_name="us-east-1@example.com/"
+        )
+
+
+def test_get_aws_region_name_for_non_llm_api_calls_rejects_malformed_env():
+    """
+    A malformed AWS_REGION / AWS_REGION_NAME env value must be rejected on the
+    non-LLM path too — Guardrails and Vector Stores read the same env vars.
+    """
+    base_aws_llm = BaseAWSLLM()
+
+    with patch("litellm.llms.bedrock.base_aws_llm.get_secret") as mock_get_secret:
+
+        def side_effect(key, default=None):
+            if key == "AWS_REGION_NAME":
+                return "us-east-1@example.com/"
+            return default
+
+        mock_get_secret.side_effect = side_effect
+
+        with pytest.raises(ValueError, match="Invalid AWS region format"):
+            base_aws_llm.get_aws_region_name_for_non_llm_api_calls()
+
+
+def test_get_aws_region_name_for_non_llm_api_calls_accepts_valid_region():
+    """The non-LLM helper still returns valid regions unchanged."""
+    base_aws_llm = BaseAWSLLM()
+    assert (
+        base_aws_llm.get_aws_region_name_for_non_llm_api_calls(
+            aws_region_name="us-east-1"
+        )
+        == "us-east-1"
+    )
+
+
+def test_get_aws_region_from_model_arn_rejects_malformed_region():
+    """
+    If the region segment of a model ARN does not match the expected format,
+    the helper must return None so the caller falls back to env / default.
+    """
+    base_aws_llm = BaseAWSLLM()
+
+    bad_arn = (
+        "arn:aws:bedrock:us-east-1@example.com:123456789012"
+        ":foundation-model/anthropic.claude-3-sonnet"
+    )
+    assert base_aws_llm._get_aws_region_from_model_arn(bad_arn) is None
+
+    good_arn = (
+        "arn:aws:bedrock:us-east-1:123456789012"
+        ":foundation-model/anthropic.claude-3-sonnet"
+    )
+    assert base_aws_llm._get_aws_region_from_model_arn(good_arn) == "us-east-1"
+
+
 def test_sign_request_with_env_var_bearer_token():
     # Create instance of actual class
     llm = BaseAWSLLM()