After differential fuzzing using bitcoinfuzz with NBitcoin, rust-miniscript and Bitcoin Core, I discovered that NBitcoin fails to parse valid Taproot descriptors containing uppercase hex characters in the internal key, breaking compatibility with Bitcoin Core and rust-miniscript.
Reproduction
This valid Taproot descriptor fails:
tr(01b2b2472Dbbbbbbbbbcbbbbbcbbbbbbcbbbbbbbbbbbbbcbbbbbbbbbbbbcbbbb)
Root Cause
The hex parser in Parse.cs line 8 only accepts lowercase hex:
private const string ValidHex = "0123456789abcdef"; // Missing A-F
When parsing the Taproot internal key (x-only pubkey), PPubkeyXOnly() uses Parse.Hex.Repeat(64) which rejects uppercase hex characters.
After differential fuzzing using bitcoinfuzz with NBitcoin, rust-miniscript and Bitcoin Core, I discovered that NBitcoin fails to parse valid Taproot descriptors containing uppercase hex characters in the internal key, breaking compatibility with Bitcoin Core and rust-miniscript.
Reproduction
This valid Taproot descriptor fails:
Root Cause
The hex parser in Parse.cs line 8 only accepts lowercase hex:
When parsing the Taproot internal key (x-only pubkey),
PPubkeyXOnly()usesParse.Hex.Repeat(64)which rejects uppercase hex characters.