nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation

nimiq-block contains block primitives to be used in Nimiq's Rust implementation. `SkipBlockProof::verify` computes its quorum check using `BitSet.len()`, then iterates `BitSet` indices and casts each `usize` index to `u16` (`slot as u16`) for slot lookup. Prior to version 1.3.0, if an attacker can get a `SkipBlockProof` verified where `MultiSignature.signers` contains out-of-range indices spaced by 65536, these indices inflate `len()` but collide onto the same in-range `u16` slot during aggregation. This makes it possible for a malicious validator with far fewer than `2f+1` real signer slots to pass skip block proof verification by multiplying a single BLS signature by the same factor. The patch for this vulnerability is included as part of v1.3.0. No known workarounds are available.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H

输入验证不恰当

Nimiq 输入验证错误漏洞

Nimiq是Nimiq开源的一个Albatross协议的Rust实现。 Nimiq 1.3.0之前版本存在输入验证错误漏洞，该漏洞源于nimiq-block中SkipBlockProof::verify使用BitSet.len()计算法定人数检查，然后迭代BitSet索引并将每个usize索引转换为u16进行插槽查找，如果攻击者能让MultiSignature.signers包含间隔65536的超范围索引，这些索引会增大len()但在聚合期间碰撞到同一范围内u16插槽，使得恶意验证者可用远少于2f+1个真

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