diff --git a/lib/crewai/src/crewai/agents/agent_builder/base_agent.py b/lib/crewai/src/crewai/agents/agent_builder/base_agent.py
index ded6bb40ab..f0e2b76c44 100644
--- a/lib/crewai/src/crewai/agents/agent_builder/base_agent.py
+++ b/lib/crewai/src/crewai/agents/agent_builder/base_agent.py
@@ -58,6 +58,13 @@
     from crewai.state.runtime import RuntimeState
 
 
+# Upper bound for agent iteration count. Prevents denial-of-wallet attacks
+# where a misconfigured or malicious `max_iter` value (e.g. 10_000_000) would
+# burn unbounded API credits. The default of 25 is unchanged; no legitimate
+# workflow needs more than 500 iterations.
+MAX_ITER_CEILING: Final[int] = 500
+
+
 def _validate_crew_ref(value: Any) -> Any:
     return value
 
@@ -284,7 +291,10 @@ class BaseAgent(BaseModel, ABC, metaclass=AgentMeta):
         default_factory=list, description="Tools at agents' disposal"
     )
     max_iter: int = Field(
-        default=25, description="Maximum iterations for an agent to execute a task"
+        default=25,
+        gt=0,
+        le=MAX_ITER_CEILING,
+        description="Maximum iterations for an agent to execute a task",
     )
     agent_executor: Annotated[
         SerializeAsAny[BaseAgentExecutor] | None,
diff --git a/lib/crewai/src/crewai/agents/agent_builder/base_agent_executor.py b/lib/crewai/src/crewai/agents/agent_builder/base_agent_executor.py
index d251b1d36e..5397a9fdb3 100644
--- a/lib/crewai/src/crewai/agents/agent_builder/base_agent_executor.py
+++ b/lib/crewai/src/crewai/agents/agent_builder/base_agent_executor.py
@@ -24,7 +24,7 @@ class BaseAgentExecutor(BaseModel):
     agent: BaseAgent | None = Field(default=None, exclude=True)
     task: Task | None = Field(default=None, exclude=True)
     iterations: int = Field(default=0)
-    max_iter: int = Field(default=25)
+    max_iter: int = Field(default=25, gt=0, le=500)
     messages: list[LLMMessage] = Field(default_factory=list)
     _resuming: bool = PrivateAttr(default=False)
 
diff --git a/lib/crewai/src/crewai/experimental/agent_executor.py b/lib/crewai/src/crewai/experimental/agent_executor.py
index 0ecd8e63a4..f40e553628 100644
--- a/lib/crewai/src/crewai/experimental/agent_executor.py
+++ b/lib/crewai/src/crewai/experimental/agent_executor.py
@@ -184,7 +184,7 @@ class AgentExecutor(Flow[AgentExecutorState], BaseAgentExecutor):
     prompt: SystemPromptResult | StandardPromptResult | None = Field(
         default=None, exclude=True
     )
-    max_iter: int = Field(default=25, exclude=True)
+    max_iter: int = Field(default=25, gt=0, le=500, exclude=True)
     tools: list[CrewStructuredTool] = Field(default_factory=list, exclude=True)
     tools_names: str = Field(default="", exclude=True)
     stop_words: list[str] = Field(default_factory=list, exclude=True)
diff --git a/lib/crewai/src/crewai/flow/runtime/__init__.py b/lib/crewai/src/crewai/flow/runtime/__init__.py
index b28eb5429d..7f4bc04fc6 100644
--- a/lib/crewai/src/crewai/flow/runtime/__init__.py
+++ b/lib/crewai/src/crewai/flow/runtime/__init__.py
@@ -28,6 +28,7 @@
     Annotated,
     Any,
     ClassVar,
+    Final,
     Generic,
     Literal,
     ParamSpec,
@@ -166,6 +167,13 @@
 logger = logging.getLogger(__name__)
 
 
+# Upper bound on router hops within a single _route() invocation. Guards
+# against circular @router definitions that would otherwise spin the event
+# loop indefinitely. No legitimate flow exceeds this; if hit, surface a
+# RuntimeError so the cycle is diagnosable instead of silently hanging.
+MAX_ROUTER_HOPS: Final[int] = 100
+
+
 def _condition_branches(
     condition: dict[str, Any],
 ) -> tuple[Literal["and", "or"], list[FlowDefinitionCondition]]:
@@ -2734,8 +2742,15 @@ async def _execute_listeners(
         current_trigger = trigger_method
         current_result = result  # Track the result to pass to each router
         current_triggering_event_id = triggering_event_id
+        hop_count = 0
 
         while True:
+            hop_count += 1
+            if hop_count > MAX_ROUTER_HOPS:
+                raise RuntimeError(
+                    f"Flow router cycle detected: exceeded {MAX_ROUTER_HOPS} "
+                    "router hops. Check for circular @router definitions."
+                )
             routers_triggered = self._find_triggered_methods(
                 current_trigger, router_only=True
             )