diff --git a/src/libxrpl/tx/Transactor.cpp b/src/libxrpl/tx/Transactor.cpp
index 7af96d3f4b..47c76cecd7 100644
--- a/src/libxrpl/tx/Transactor.cpp
+++ b/src/libxrpl/tx/Transactor.cpp
@@ -181,15 +181,13 @@ Transactor::preflight1(PreflightContext const& ctx, std::uint32_t flagMask)
     if (ctx.tx.isFlag(tfInnerBatchTxn) && !ctx.rules.enabled(featureBatchV1_1))
         return temINVALID_FLAG;
 
-    if (ctx.rules.enabled(featureBatchV1_1) &&
-        ctx.tx.isFlag(tfInnerBatchTxn) != ctx.parentBatchId.has_value())
+    // Reject if the inner batch flag and parentBatchId are inconsistent.
+    // A standalone tx with tfInnerBatchTxn but no parentBatchId is an
+    // attack attempt. A tx with parentBatchId but without tfInnerBatchTxn
+    // is a programming error.
+    if (ctx.tx.isFlag(tfInnerBatchTxn) != ctx.parentBatchId.has_value())
         return temINVALID_INNER_BATCH;
 
-    XRPL_ASSERT(
-        ctx.tx.isFlag(tfInnerBatchTxn) == ctx.parentBatchId.has_value() ||
-            !ctx.rules.enabled(featureBatchV1_1),
-        "Inner batch transaction must have a parent batch ID.");
-
     return tesSUCCESS;
 }
 
@@ -204,15 +202,18 @@ Transactor::preflight2(PreflightContext const& ctx)
         return *ret;
     }
 
-    // It should be impossible for the InnerBatchTxn flag to be set without
-    // featureBatchV1_1 being enabled
-    XRPL_ASSERT_PARTS(
-        !ctx.tx.isFlag(tfInnerBatchTxn) || ctx.rules.enabled(featureBatchV1_1),
-        "xrpl::Transactor::preflight2",
-        "InnerBatch flag only set if feature enabled");
-    // Skip signature check on batch inner transactions
-    if (ctx.tx.isFlag(tfInnerBatchTxn) && ctx.rules.enabled(featureBatchV1_1))
+    // Skip signature check on batch inner transactions, but only if
+    // this tx was actually submitted through the batch apply path
+    // (parentBatchId is set). Without this check, a standalone tx
+    // with tfInnerBatchTxn could bypass signature verification.
+    if (ctx.tx.isFlag(tfInnerBatchTxn))
+    {
+        if (!ctx.rules.enabled(featureBatchV1_1))
+            return temINVALID_FLAG;
+        if (!ctx.parentBatchId.has_value())
+            return temINVALID_INNER_BATCH;
         return tesSUCCESS;
+    }
     // Do not add any checks after this point that are relevant for
     // batch inner transactions. They will be skipped.
 
diff --git a/src/test/app/Batch_test.cpp b/src/test/app/Batch_test.cpp
index 143ecaa241..9e35d49fcc 100644
--- a/src/test/app/Batch_test.cpp
+++ b/src/test/app/Batch_test.cpp
@@ -4411,6 +4411,53 @@ class Batch_test : public beast::unit_test::suite
         }
     }
 
+    void
+    testStandaloneInnerBatchFlag(FeatureBitset features)
+    {
+        testcase("standalone tx with tfInnerBatchTxn rejected");
+
+        using namespace test::jtx;
+        using namespace std::literals;
+
+        // A standalone Payment with tfInnerBatchTxn must be rejected.
+        // Without proper guards this would bypass signature verification
+        // in preflight2.
+        {
+            test::jtx::Env env{*this, features};
+
+            auto const alice = Account("alice");
+            auto const bob = Account("bob");
+            env.fund(XRP(10000), alice, bob);
+            env.close();
+
+            // Submit a normal Payment with tfInnerBatchTxn flag.
+            // preflight1 must reject with temINVALID_INNER_BATCH because
+            // the flag is set but no parentBatchId exists.
+            env(pay(alice, bob, XRP(1)), txflags(tfInnerBatchTxn), ter(telENV_RPC_FAILED));
+            env.close();
+
+            // Verify via direct apply path (bypassing RPC layer)
+            env.app().openLedger().modify([&](OpenView& view, beast::Journal j) {
+                // Construct a Payment STTx with tfInnerBatchTxn,
+                // empty signing pub key, and no signature — mimicking
+                // what an attacker would send to skip sig verification.
+                STTx const stx = STTx(ttPAYMENT, [&](auto& obj) {
+                    obj.setAccountID(sfAccount, alice.id());
+                    obj.setAccountID(sfDestination, bob.id());
+                    obj.setFieldAmount(sfAmount, XRP(1));
+                    obj.setFieldAmount(sfFee, XRP(0));
+                    obj.setFieldU32(sfSequence, env.seq(alice));
+                    obj.setFieldU32(sfFlags, tfInnerBatchTxn);
+                });
+
+                auto const result = xrpl::apply(env.app(), view, stx, tapNONE, j);
+                // Must NOT be applied — signature was never checked
+                BEAST_EXPECT(!result.applied);
+                return false;
+            });
+        }
+    }
+
     void
     testWithFeats(FeatureBitset features)
     {
@@ -4445,6 +4492,7 @@ class Batch_test : public beast::unit_test::suite
         testBatchDelegate(features);
         testValidateRPCResponse(features);
         testBatchCalculateBaseFee(features);
+        testStandaloneInnerBatchFlag(features);
     }
 
 public: