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CVE-2026-33471— nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation

Quick assessment

Affected
nimiq nimiq-block
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

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

CVSS 9.6 · Critical EPSS 0.29% · P20

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-33471

Vulnerability Information
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Vulnerability Title
nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Nimiq 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
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
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

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Affected Products

Vendor Product Affected Versions CPE Subscribe
nimiq nimiq-block < 1.3.0 -

II. Public POCs for CVE-2026-33471

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III. Intelligence Information for CVE-2026-33471

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Patches & Fixes for CVE-2026-33471 (1)

Vendor Advisories for CVE-2026-33471 (1)

Same Patch Batch · nimiq · 2026-04-22 · 8 CVEs total

CVE-2026-34063 7.5 HIGH network-libp2p: Peer can crash the node by opening discovery protocol substream twice
CVE-2026-34065 7.5 HIGH nimiq-primitives: Node crash due to missing interlink validation in election macro block p
CVE-2026-34068 6.8 MEDIUM nimiq-transaction: UpdateValidator transactions allows voting key change without proof-of-
CVE-2026-34062 5.3 MEDIUM Nimiq has Allocation of Resources Without Limits or Throttling in its libp2p request/respo
CVE-2026-34064 5.3 MEDIUM nimiq-account: Vesting insufficient funds error can panic
CVE-2026-34066 5.3 MEDIUM nimiq-blockchain: Peer-triggerable panic during history sync
CVE-2026-34067 3.1 LOW nimiq-transaction vulnerable to panic via `HistoryTreeProof` length mismatch

IV. Related Vulnerabilities

Same vendor: nimiq
Same weakness: CWE-20

V. Comments for CVE-2026-33471

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