Summary

ParseRFC6187 in examples/client/common.c read the peer-supplied RFC6187 name length l with ato32() and then advanced m += l + sizeof(word32) without validating l against inSz. Because l is attacker-controlled (the leading length field of the SSH host-key blob), a value larger than inSz pushed m past inSz. The subsequent inSz - m unsigned subtraction then underflowed to a large value, so the < sizeof(word32) bounds test passed and ato32(in + m, &count) read past the end of the pubKey buffer.

This adds the same bounds check the sibling apps/wolfssh/common.c copy already has, restoring parity between the two implementations.

Addressed by f_6267.

Changes

• examples/client/common.c: in ParseRFC6187, reject l > inSz - sizeof(word32) with WS_BUFFER_E immediately after reading l, before computing m.

/* Skip the name */
ato32(in, &l);
if (l > inSz - sizeof(word32))
    return WS_BUFFER_E;

m += l + sizeof(word32);

Why it is correct

• The earlier inSz < sizeof(word32) check guarantees inSz - sizeof(word32) cannot underflow.
• Rejecting oversized l keeps m <= inSz, so the later inSz - m subtractions stay in range and the existing bounds tests work as intended.