Litecoin Core version 0.21.5.5 is now available from:

https://download.litecoin.org/litecoin-0.21.5.5/.

This is a patch version release that includes important MWEB consensus hardening, node reliability improvements, wallet and mining fixes, and build/test updates. This release includes important security updates. All node operators and wallet users are strongly encouraged to upgrade ASAP.

Please report bugs using the issue tracker at GitHub:

https://github.com/litecoin-project/litecoin/issues

Notable changes

Important MWEB updates

This release contains important MWEB validation and state-handling fixes.
Upgrading is recommended for all users, especially miners, pools, and nodeoperators using MWEB.

• Added additional validation for MWEB inputs, pegins, HogEx data, kernel fees, and kernel lock heights (e7cbf1d, 42e7071, 8f8ad64, b9bd99a, 7564f05, a549004).
• Hardened MWEB amount and fee calculations against overflow and invalid edge cases (42e7071, 1cd94bb).
• Added fallback handling for rare hash-to-secret-key cases so derived MWEB keys are valid scalars (773c138).
• Added consensus parameters for known frozen or approved MWEB transactions and outputs needed to keep MWEB state balanced (1dcbf3f, 17f16ce, 66f6856).
• Improved handling of mutated or invalid MWEB block data so invalid data does not leave stale block data or mutate cached chainstate (742ee94, ff309cd, 17f16ce).
• Updated MWEB chainstate during block replay and crash recovery (bbd3b78).

Network and policy changes

• Increased the maximum P2P protocol message length to 32 MB so valid MWEB blocks and messages fit under the message-size limit (457bcd7).
• Enforced standard script policy checks for pegout scripts (c25bf89).

Mining changes

• Avoid reading the previous block from disk when constructing HogEx transactions; use MWEB data already stored in the block index (873d9d2).
• Improved getblocktemplate fee and sigop accounting for transactions carrying MWEB data (873d9d2).
• Avoid including MWEB transactions in candidate blocks when their input and output commitments would sum to zero (f423a84).

Wallet and RPC changes

• Fixed MWEB balance and pegout accounting (1dcbf3f, 1cc1cee).
• Added MWEB view keys to dumpwallet (eae9e47).
• Supported maxfeerate=0 for MWEB transactions in sendrawtransaction and testmempoolaccept (8782ab9).
• Allowed getblocktemplate on test chains when the node is unconnected or in initial block download (455aff8).

Bug fixes

• Fixed MWEB PMMR rewind corruption and improved MMR file write durability (23e5eac, bf25a7c, 3110a7e).
• Fixed a cache leaf bounds check (6dd2952).
• Fixed a transaction index consistency issue that could occur if writing block data failed after the index commit (eb7f68a).
• Fixed wallet loading with Boost 1.78 and newer (3c3aedb, c882663).
• Fixed a debug build logger symbol conflict and made MWEB logger initialization safer (6fc0530, b4c0037).

Build and test changes

• Added missing <cstdint> includes needed by some compilers (58f89ba).
• Replaced the functional test dependency on the external litecoin_scrypt Python package (d139222).
• Added and expanded tests for MWEB P2P messages, duplicate pegins, crash recovery, mutated blocks, mining, and wallet/RPC behavior.
• Normalized line endings in selected documentation, Qt resources, and fuzz test files (dcc7bc5).
• Fixed the broken Transifex link in the README (0f5f7d5).

Hashes for verification

These are the SHA-256 hashes of the released files:

3561a1f0ff8db311e4f18553020f625d5547f5bfe9eade8671b9c63aa5f7462a  litecoin-0.21.5.5-aarch64-linux-gnu.tar.gz
a117a3f8f699b85cb551f318d37cd06d43839b81a658e39287c2c511e6d51bd9  litecoin-0.21.5.5-arm-linux-gnueabihf.tar.gz
0f4c9bd28bb17680c9a68f8244da03d899634cb9470c2fa18ab16ce53d44993a  litecoin-0.21.5.5-riscv64-linux-gnu.tar.gz
623410d4f2695a68aa71332ae0672fee19276f41c1c63a531f97e24a50edde14  litecoin-0.21.5.5-x86_64-linux-gnu.tar.gz
f522e6f93a48a884a0a536e1f1785b5daaed21abcd5b8c46cd9c9046d7e727d9  litecoin-osx-signed.dmg#
9d222bf96eed1c209e4f57b278f11d9a5266fb2c6caedc23c4a8f4b421288c70  litecoin-0.21.5.5-win64-setup.exe

Credits

Thanks to everyone who directly contributed to this release:

• David Burkett
• Loshan