diff --git a/spring-web/src/main/java/org/springframework/http/codec/protobuf/ProtobufDecoder.java b/spring-web/src/main/java/org/springframework/http/codec/protobuf/ProtobufDecoder.java
index 9d0db71396..8d9ba54d90 100644
--- a/spring-web/src/main/java/org/springframework/http/codec/protobuf/ProtobufDecoder.java
+++ b/spring-web/src/main/java/org/springframework/http/codec/protobuf/ProtobufDecoder.java
@@ -172,6 +172,8 @@ public class ProtobufDecoder extends ProtobufCodecSupport implements Decoder<Mes
 
 		private int messageBytesToRead;
 
+		private int offset;
+
 
 		public MessageDecoderFunction(ResolvableType elementType, int maxMessageSize) {
 			this.elementType = elementType;
@@ -188,11 +190,9 @@ public class ProtobufDecoder extends ProtobufCodecSupport implements Decoder<Mes
 
 				do {
 					if (this.output == null) {
-						int firstByte = input.read();
-						if (firstByte == -1) {
-							throw new DecodingException("Cannot parse message size");
+						if (!readMessageSize(input)) {
+							return messages;
 						}
-						this.messageBytesToRead = CodedInputStream.readRawVarint32(firstByte, input.asInputStream());
 						if (this.messageBytesToRead > this.maxMessageSize) {
 							throw new DecodingException(
 									"The number of bytes to read from the incoming stream " +
@@ -235,6 +235,57 @@ public class ProtobufDecoder extends ProtobufCodecSupport implements Decoder<Mes
 				DataBufferUtils.release(input);
 			}
 		}
+
+		/**
+		 * Parse message size as a varint from the input stream, updating {@code messageBytesToRead} and
+		 * {@code offset} fields if needed to allow processing of upcoming chunks.
+		 * Inspired from {@link CodedInputStream#readRawVarint32(int, java.io.InputStream)}
+		 *
+		 * @return {code true} when the message size is parsed successfully, {code false} when the message size is
+		 * truncated
+		 * @see <a href ="https://developers.google.com/protocol-buffers/docs/encoding#varints">Base 128 Varints</a>
+		 */
+		private boolean readMessageSize(DataBuffer input) {
+			if (this.offset == 0) {
+				if (input.readableByteCount() == 0) {
+					return false;
+				}
+				int firstByte = input.read();
+				if ((firstByte & 0x80) == 0) {
+					this.messageBytesToRead = firstByte;
+					return true;
+				}
+				this.messageBytesToRead = firstByte & 0x7f;
+				this.offset = 7;
+			}
+
+			if (this.offset < 32) {
+				for (; this.offset < 32; this.offset += 7) {
+					if (input.readableByteCount() == 0) {
+						return false;
+					}
+					final int b = input.read();
+					this.messageBytesToRead |= (b & 0x7f) << offset;
+					if ((b & 0x80) == 0) {
+						this.offset = 0;
+						return true;
+					}
+				}
+			}
+			// Keep reading up to 64 bits.
+			for (; this.offset < 64; this.offset += 7) {
+				if (input.readableByteCount() == 0) {
+					return false;
+				}
+				final int b = input.read();
+				if ((b & 0x80) == 0) {
+					this.offset = 0;
+					return true;
+				}
+			}
+			this.offset = 0;
+			throw new DecodingException("Cannot parse message size: malformed varint");
+		}
 	}
 
 }
diff --git a/spring-web/src/test/java/org/springframework/http/codec/protobuf/ProtobufDecoderTests.java b/spring-web/src/test/java/org/springframework/http/codec/protobuf/ProtobufDecoderTests.java
index d8796026ec..7d0be96995 100644
--- a/spring-web/src/test/java/org/springframework/http/codec/protobuf/ProtobufDecoderTests.java
+++ b/spring-web/src/test/java/org/springframework/http/codec/protobuf/ProtobufDecoderTests.java
@@ -128,7 +128,9 @@ public class ProtobufDecoderTests extends AbstractDecoderTestCase<ProtobufDecode
 	}
 
 	@Test
-	public void decodeSplitChunks() throws IOException {
+	public void decodeSplitChunks() {
+
+
 		Flux<DataBuffer> input = Flux.just(this.testMsg1, this.testMsg2)
 				.flatMap(msg -> Mono.defer(() -> {
 					DataBuffer buffer = this.bufferFactory.allocateBuffer();
@@ -158,6 +160,44 @@ public class ProtobufDecoderTests extends AbstractDecoderTestCase<ProtobufDecode
 				.verifyComplete());
 	}
 
+	@Test  // SPR-17429
+	public void decodeSplitMessageSize() {
+		this.decoder.setMaxMessageSize(100009);
+		StringBuilder builder = new StringBuilder();
+		for (int i = 0; i < 10000; i++) {
+			builder.append("azertyuiop");
+		}
+		Msg bigMessage = Msg.newBuilder().setFoo(builder.toString()).setBlah(secondMsg2).build();
+
+		Flux<DataBuffer> input = Flux.just(bigMessage, bigMessage)
+				.flatMap(msg -> Mono.defer(() -> {
+					DataBuffer buffer = this.bufferFactory.allocateBuffer();
+					try {
+						msg.writeDelimitedTo(buffer.asOutputStream());
+						return Mono.just(buffer);
+					}
+					catch (IOException e) {
+						release(buffer);
+						return Mono.error(e);
+					}
+				}))
+				.flatMap(buffer -> {
+					int len = 2;
+					Flux<DataBuffer> result = Flux.just(
+							DataBufferUtils.retain(buffer.slice(0, len)),
+							DataBufferUtils
+									.retain(buffer.slice(len, buffer.readableByteCount() - len))
+					);
+					release(buffer);
+					return result;
+				});
+
+		testDecode(input, Msg.class, step -> step
+				.expectNext(bigMessage)
+				.expectNext(bigMessage)
+				.verifyComplete());
+	}
+
 	@Test
 	public void decodeMergedChunks() throws IOException {
 		DataBuffer buffer = this.bufferFactory.allocateBuffer();