Maven · io.netty.incubator:netty-incubator-codec-bhttp
netty-incubator-codec-ohttp: Binary HTTP parser unchecked varint length overflow causes decoder crash
io.netty.incubator:netty-incubator-codec-bhttp uses attacker-controlled Binary HTTP variable-length integers as long values but accumulates them into int offsets. Large valid varint lengths wrap the internal offset negative, leading to unchecked ArrayIndexOutOfBoundsException / IndexOutOfBoundsException from a tiny malformed BHTTP payload. A remote peer can trigger connection-level denial of service in applications that expose BinaryHttpParser / BinaryHttpDecoder to untrusted input.
In codec-bhttp/src/main/java/io/netty/incubator/codec/bhttp/BinaryHttpParser.java, several parser paths store cumulative byte offsets in int sumBytes and then add attacker-controlled long lengths using compound assignment. In Java, int += long narrows the result back to int, so a length such as 2^31 wraps sumBytes negative.
Primary request-control-data path:
readRequestHead(...) declares int sumBytes = 0 at BinaryHttpParser.java:386.methodLength as a long at BinaryHttpParser.java:394.sumBytes += methodLength at BinaryHttpParser.java:395, narrowing the result to int.methodLength is 2^31, sumBytes wraps negative and bypasses if (sumBytes >= in.readableBytes()) return null at BinaryHttpParser.java:396-398.schemeLengthIdx = in.readerIndex() + sumBytes and calls in.getByte(schemeLengthIdx) at BinaryHttpParser.java:401-402, producing a negative index exception.The same pattern is present in header parsing:
readFieldLine(...) uses int sumBytes and adds long nameLength / long valueLength at BinaryHttpParser.java:659-680.valueLengthIdx = nameIdx + (int) nameLength at BinaryHttpParser.java:674 can also overflow.getIndeterminateLength(...) similarly uses int sumBytes and long possibleTerminator at BinaryHttpParser.java:544-553.
Safe local verification performed in this repository. After compiling codec-bhttp, the following minimal verifier uses a 15-byte payload:
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.incubator.codec.bhttp.BinaryHttpParser;
public final class VerifyBhttpOverflow {
public static void main(String[] args) {
byte[] payload = new byte[] {
0x00, (byte)0xc0, 0x00, 0x00, 0x00, (byte)0x80, 0x00, 0x00, 0x00,
0x47, 0x45, 0x54, 0x58, 0x58, 0x58
};
ByteBuf input = Unpooled.wrappedBuffer(payload);
try {
new BinaryHttpParser(8192).parse(input, false);
System.out.println("returned");
} catch (Throwable t) {
System.out.println(t.getClass().getName());
System.out.println(t.getMessage());
}
}
}
Payload interpretation:
00: known-length request frame indicator.c000000080000000: valid 8-byte varint encoding of 0x80000000 (2^31) as the method length.474554585858: a few dummy bytes so the parser proceeds far enough to compute the next index.Observed result:
java.lang.ArrayIndexOutOfBoundsException
Index -2147483639 out of bounds for length 15
The parser should reject the malformed/incomplete message with a controlled decoder exception or return null awaiting more bytes; it should not allow integer wraparound to reach unchecked buffer indexing.
A remote peer can trigger an unchecked exception in the Binary HTTP decoder using a tiny payload. In typical Netty pipelines this closes or fails the affected channel. Depending on application-level exception handling, repeated payloads can cause sustained denial of service for exposed BHTTP endpoints. No memory corruption or information disclosure was observed because the failure occurs in Java/Netty bounds checks.
long for all cumulative byte counts derived from protocol lengths.int, verify it is non-negative, no larger than Integer.MAX_VALUE, and no larger than available readable bytes and configured limits.sumBytes >= in.readableBytes() checks with precise checked arithmetic that permits exact-boundary complete fields but rejects impossible lengths.CorruptedFrameException / TooLongFrameException for invalid or unsupported lengths.Integer.MAX_VALUE in request control data, response control data, known and indeterminate field sections, and field lines.codec-bhttp/src/main/java/io/netty/incubator/codec/bhttp/BinaryHttpParser.java:386-402codec-bhttp/src/main/java/io/netty/incubator/codec/bhttp/BinaryHttpParser.java:659-680codec-bhttp/src/main/java/io/netty/incubator/codec/bhttp/BinaryHttpParser.java:544-553Is your project exposed to this? Stateward checks every dependency on every pull request and flags it only if your code actually reaches it.
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