SENDCMPCT announce field is not validated against BIP152 (MUST be 0 or 1) #35542

issue brunoerg opened this issue on June 16, 2026

brunoerg commented at 1:49 PM on June 16, 2026: contributor
When processing a sendcmpct message, the first field (the high-bandwidth announce boolean) is not validated to be 0 or 1. Any non-zero byte is silently accepted and treated as true, which deviates from what the BIP152 says: "The first integer SHALL be interpreted as a boolean (and MUST have a value of either 1 or 0)".
```
if (msg_type == NetMsgType::SENDCMPCT) {
    bool sendcmpct_hb{false};
    uint64_t sendcmpct_version{0};
    vRecv >> sendcmpct_hb >> sendcmpct_version;

    // Only support compact block relay with witnesses
    if (sendcmpct_version != CMPCTBLOCKS_VERSION) return;
```
Not super relevant in practice, but just a divergence with the BIP that we noticed while reviewing another impl of compact blocks (cc @MPins).
yancyribbens commented at 3:16 PM on June 16, 2026: contributor

This is I believe the same change I applied in rust-bitcoin https://github.com/rust-bitcoin/rust-bitcoin/pull/6317

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