diff --git a/src/brpc/amf.cpp b/src/brpc/amf.cpp
index 290ce64258..7af43c08f2 100644
--- a/src/brpc/amf.cpp
+++ b/src/brpc/amf.cpp
@@ -392,6 +392,12 @@ bool ReadAMFUint32(uint32_t* val, AMFInputStream* stream) {
     if (!ReadAMFNumber(&d, stream)) {
         return false;
     }
+    // The number comes from the peer and may be NaN or out of [0, UINT32_MAX],
+    // for which the conversion below is undefined. The check is false for NaN.
+    if (!(d >= 0.0 && d <= 4294967295.0)) {
+        LOG(ERROR) << "Invalid AMF number=" << d << " for uint32";
+        return false;
+    }
     *val = (uint32_t)d;
     return true;
 }
diff --git a/test/brpc_rtmp_unittest.cpp b/test/brpc_rtmp_unittest.cpp
index da2e77af2b..326441204e 100644
--- a/test/brpc_rtmp_unittest.cpp
+++ b/test/brpc_rtmp_unittest.cpp
@@ -19,6 +19,7 @@
 
 // Date: Fri May 20 15:52:22 CST 2016
 
+#include <limits>
 #include <sys/ioctl.h>
 #include <sys/types.h>
 #include <sys/socket.h>
@@ -734,6 +735,44 @@ TEST(RtmpTest, amf) {
     ASSERT_EQ("heheda", info3.description());
 }
 
+TEST(RtmpTest, amf_rejects_out_of_range_uint32) {
+    // Each value below encodes legally in an AMF0 number but has no uint32
+    // representation; the cast in ReadAMFUint32 was undefined for them.
+    const double bad_values[] = { -1.0, 4294967296.0, 1e30, -1e30,
+                                  std::numeric_limits<double>::infinity(),
+                                  std::numeric_limits<double>::quiet_NaN() };
+    for (size_t i = 0; i < arraysize(bad_values); ++i) {
+        std::string buf;
+        {
+            google::protobuf::io::StringOutputStream zc_stream(&buf);
+            brpc::AMFOutputStream ostream(&zc_stream);
+            brpc::WriteAMFNumber(bad_values[i], &ostream);
+            ASSERT_TRUE(ostream.good());
+        }
+        google::protobuf::io::ArrayInputStream zc_stream(buf.data(), buf.size());
+        brpc::AMFInputStream istream(&zc_stream);
+        uint32_t val = 0;
+        EXPECT_FALSE(brpc::ReadAMFUint32(&val, &istream)) << "i=" << i;
+    }
+
+    const double good_values[] = { 0.0, 42.5, 4294967295.0 };
+    const uint32_t expected_values[] = { 0, 42, 4294967295u };
+    for (size_t i = 0; i < arraysize(good_values); ++i) {
+        std::string buf;
+        {
+            google::protobuf::io::StringOutputStream zc_stream(&buf);
+            brpc::AMFOutputStream ostream(&zc_stream);
+            brpc::WriteAMFNumber(good_values[i], &ostream);
+            ASSERT_TRUE(ostream.good());
+        }
+        google::protobuf::io::ArrayInputStream zc_stream(buf.data(), buf.size());
+        brpc::AMFInputStream istream(&zc_stream);
+        uint32_t val = 0;
+        ASSERT_TRUE(brpc::ReadAMFUint32(&val, &istream)) << "i=" << i;
+        ASSERT_EQ(expected_values[i], val);
+    }
+}
+
 TEST(RtmpTest, amf_rejects_oversized_string_before_growing_output) {
     std::string req_buf;
     AppendAMFLongStringHeader(&req_buf, 16);