CVE-2026-33471
CRITICALCVE-2026-33471 is a critical-severity (CVSS 9.6) Improper Input Validation vulnerability in nimiq-block. O3 Security confirms whether CVE-2026-33471 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation
Blast Radius
nimiq-blockReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | nimiq-block | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nimiq-block. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of nimiq-block has shipped for CVE-2026-33471 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-33471 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-33471. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-33471 in your dependencies?
O3 detects CVE-2026-33471 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.