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inspector: fix out-of-bounds read in ws frame decoding #64618

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inspector: fix out-of-bounds read in ws frame decoding #64618

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bfe6764
inspector: fix out-of-bounds read in ws frame decoding
Nashit-h Jul 20, 2026
1958e12
inspector: simplify ws length guard, make test fail without fix
Nashit-h Jul 22, 2026
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5 changes: 4 additions & 1 deletion src/inspector_socket.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -360,7 +360,10 @@ static ws_decode_result decode_frame_hybi17(const std::vector<char>& buffer,
}
size_t payload_length = static_cast<size_t>(payload_length64);

if (buffer.size() - kMaskingKeyWidthInBytes < payload_length)
// The masking key and the payload follow the header `it` already walked
// past, so they have to fit in what is left rather than in the whole buffer.
size_t remaining = static_cast<size_t>(buffer.end() - it);
if (remaining < kMaskingKeyWidthInBytes + payload_length)
return FRAME_INCOMPLETE;

std::vector<char>::const_iterator masking_key = it;
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25 changes: 25 additions & 0 deletions test/cctest/test_inspector_socket.cc
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Expand Up @@ -409,6 +409,31 @@ TEST_F(InspectorSocketTest, ReadsAndWritesInspectorMessage) {
reinterpret_cast<uv_handle_t*>(&client_socket)));
}

TEST_F(InspectorSocketTest, WaitsForFrameBodyToArrive) {

@legendecas legendecas Jul 21, 2026

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The test also passed on the main branch without the patch.

@Nashit-h Nashit-h Jul 22, 2026

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Good catch, you're right. The two do_write calls were landing in the same read, so the decoder never saw the header on its own and the bug wasn't reached. I added a server->client round trip between them, which forces the header to be read by itself; I confirmed the decoder now gets a 2 byte buffer first and an 11 byte one second.

With that, reverting the src change makes the test die with SIGBUS (exit 138) instead of passing. Full cctest run is 201/201 with the fix in place.

do_write(const_cast<char*>(HANDSHAKE_REQ), sizeof(HANDSHAKE_REQ) - 1);
expect_handshake();

// A header announcing a masked five byte payload, with the masking key and
// the payload still on the wire. The frame has to be treated as incomplete
// until the remaining bytes show up.
const char FRAME_HEADER[] = {'\x81', '\x85'};
do_write(FRAME_HEADER, sizeof(FRAME_HEADER));

// Round trip through the server so the header is guaranteed to have been
// read on its own, instead of arriving together with the body below.
const char SERVER_MESSAGE[] = "ping";
const char SERVER_FRAME[] = {'\x81', '\x04', 'p', 'i', 'n', 'g'};
delegate->Write(SERVER_MESSAGE, sizeof(SERVER_MESSAGE) - 1);
expect_on_client(SERVER_FRAME, sizeof(SERVER_FRAME));

const char FRAME_BODY[] = {'\x01', '\x02', '\x03', '\x04',
'\x69', '\x67', '\x6F', '\x68', '\x6E'};
do_write(FRAME_BODY, sizeof(FRAME_BODY));

const char CLIENT_MESSAGE[] = "hello";
delegate->ExpectData(CLIENT_MESSAGE, sizeof(CLIENT_MESSAGE) - 1);
}

TEST_F(InspectorSocketTest, BufferEdgeCases) {
do_write(const_cast<char*>(HANDSHAKE_REQ), sizeof(HANDSHAKE_REQ) - 1);
expect_handshake();
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