diff --git a/litellm/litellm_core_utils/logging_utils.py b/litellm/litellm_core_utils/logging_utils.py
index 5e247324cea..5ac6b5435dc 100644
--- a/litellm/litellm_core_utils/logging_utils.py
+++ b/litellm/litellm_core_utils/logging_utils.py
@@ -43,7 +43,7 @@ Helper utils used for logging callbacks
 
 # Regex matching data-URI base64 content: "data:<mime>;base64,<payload>"
 # Captures: group(1)=mime_type, group(2)=base64_payload
-_DATA_URI_RE: Final = re.compile(r"data:([^;]+);base64,([A-Za-z0-9+/=]+)")
+_DATA_URI_RE: Final = re.compile(r"data:([^;,\s]{1,255});base64,([A-Za-z0-9+/=]+)")
 
 # Maximum nesting depth for _truncate_base64_in_value to guard against
 # pathological payloads. OpenAI message format is typically 3-4 levels deep.
diff --git a/tests/unit/litellm_core_utils/test_logging_utils.py b/tests/unit/litellm_core_utils/test_logging_utils.py
index 7b8db097d47..edf0dc7960b 100644
--- a/tests/unit/litellm_core_utils/test_logging_utils.py
+++ b/tests/unit/litellm_core_utils/test_logging_utils.py
@@ -95,6 +95,18 @@ class TestTruncateBase64InString:
         result = _truncate_base64_in_string(text)
         assert result.count("base64_data truncated") == 2
 
+    @pytest.mark.timeout(10)
+    @pytest.mark.parametrize(
+        "text",
+        [
+            'data: {"choices": [{"delta": {"content": "hi"}}]}\n\n' * 50_000,
+            "data:" * 200_000,
+        ],
+        ids=["sse_lines", "whitespace_free_prefixes"],
+    )
+    def test_repeated_data_prefixes_without_data_uris_are_scanned_in_linear_time(self, text: str):
+        assert _truncate_base64_in_string(text) == text
+
     def test_no_data_uri(self):
         text = "hello world, no base64 here"
         assert _truncate_base64_in_string(text) == text