diff --git a/pyrit/score/response_handler.py b/pyrit/score/response_handler.py
index 0c27efd120..7aa2c012c0 100644
--- a/pyrit/score/response_handler.py
+++ b/pyrit/score/response_handler.py
@@ -5,6 +5,7 @@
 
 import abc
 import json
+import math
 from abc import abstractmethod
 from collections.abc import Sequence
 from typing import TYPE_CHECKING
@@ -146,7 +147,7 @@ class JsonSchemaResponseHandler(ResponseHandler):
     ``json.loads`` the text, then read the score value, rationale, optional description,
     category, and metadata from configurable keys. It also owns the response contract: the
     optional JSON schema handed to the target, and (when ``numeric_value`` is set) validating
-    that the parsed score value is numeric.
+    that the parsed score value is finite and numeric.
     """
 
     def __init__(
@@ -173,7 +174,8 @@ def __init__(
                 should honor. Exposed via ``response_schema`` and forwarded to the target by the
                 LLM round-trip. Defaults to None.
             numeric_value (bool): When True, ``parse`` requires the parsed score value to be
-                parsable as a float and raises ``InvalidJsonException`` otherwise. Defaults to False.
+                parsable as a finite float and raises ``InvalidJsonException`` otherwise. Defaults
+                to False.
         """
         self._score_value_output_key = score_value_output_key
         self._rationale_output_key = rationale_output_key
@@ -219,7 +221,7 @@ def parse(
                 parsed category is not a string or a list of strings.
             InvalidJsonException: If the response is invalid JSON, is not a top-level JSON object,
                 is missing a required key, or (when this handler is numeric) the score value is not
-                parsable as a float.
+                parsable as a finite float.
         """
         response_json = remove_markdown_json(response_text)
         try:
@@ -251,11 +253,15 @@ def parse(
             try:
                 # A numeric handler requires the score value to be parsable as a float; a
                 # well-formed-but-non-numeric value is treated as an invalid response.
-                float(score.raw_score_value)
+                parsed_value = float(score.raw_score_value)
             except ValueError:
                 raise InvalidJsonException(
                     message=f"Invalid JSON response, score_value should be a float not this: {score.raw_score_value}"
                 ) from None
+            if not math.isfinite(parsed_value):
+                raise InvalidJsonException(
+                    message=f"Invalid JSON response, score_value must be a finite float: {score.raw_score_value}"
+                )
 
         return score
 
diff --git a/tests/unit/score/test_response_handler.py b/tests/unit/score/test_response_handler.py
index fac1b55ac0..df82970f8d 100644
--- a/tests/unit/score/test_response_handler.py
+++ b/tests/unit/score/test_response_handler.py
@@ -22,6 +22,18 @@ def test_json_schema_response_handler_rejects_non_object_response(response_text:
         )
 
 
+@pytest.mark.parametrize("score_value", ["nan", "NaN", "inf", "-inf", "Infinity"])
+def test_json_schema_response_handler_rejects_non_finite_numeric_values(score_value: str) -> None:
+    handler = JsonSchemaResponseHandler(numeric_value=True)
+
+    with pytest.raises(InvalidJsonException, match="finite float"):
+        handler.parse(
+            response_text=f'{{"score_value": "{score_value}", "rationale": "test"}}',
+            scorer_identifier=SCORER_IDENTIFIER,
+            scored_prompt_id="test-id",
+        )
+
+
 @pytest.mark.parametrize(
     ("json_value", "expected"),
     [