While fuzzing the RPC interface I stumbled upon a signed integer overflow in CTxMemPool::PrioritiseTransaction(…) which is reachable via the following two prioritisetransaction RPC calls:
 0$ ./autogen.sh
 1$ CC=clang CXX=clang++ ./configure --with-sanitizers=address,undefined
 2$ make
 3$ UBSAN_OPTIONS="print_stacktrace=1" src/bitcoind &
 4$ src/bitcoin-cli prioritisetransaction cafebabecafebabecafebabecafebabecafebabecafebabecafebabecafebabe 0 -9123456789123456789
 5$ src/bitcoin-cli prioritisetransaction cafebabecafebabecafebabecafebabecafebabecafebabecafebabecafebabe 0 -9123456789123456789
 6txmempool.cpp:832:15: runtime error: signed integer overflow: -9123456789123456789 + -9123456789123456789 cannot be represented in type 'long'
 7    [#0](/bitcoin-bitcoin/0/) 0x5581f3e69c3c in CTxMemPool::PrioritiseTransaction(uint256 const&, long const&) src/txmempool.cpp:832:15
 8    [#1](/bitcoin-bitcoin/1/) 0x5581f3c93852 in prioritisetransaction()::$_6::operator()(RPCHelpMan const&, JSONRPCRequest const&) const src/rpc/mining.cpp:470:36
 9…
10
11SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior txmempool.cpp:832:15
Nothing high priority of course, but still worth fixing :)