# CVE-2026-34066: nimiq-blockchain: Peer-triggerable panic during history sync

> A remote peer can trigger a panic in the nimiq-blockchain library during history sync, causing a denial of service.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 22 Apr 2026
- **Updated:** 23 Apr 2026
- **Also known as:** GHSA-j99g-7rqw-q9jg

## What is CVE-2026-34066?

CVE-2026-34066 is a medium-severity denial of service vulnerability in nimiq-blockchain, published on 22 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

nimiq-blockchain provides persistent block storage for Nimiq's Rust implementation. Prior to version 1.3.0, `HistoryStore::put_historic_txns` uses an `assert!` to enforce invariants about `HistoricTransaction.block_number` (must be within the macro block being pushed and within the same epoch). During history sync, a peer can influence the `history: &[HistoricTransaction]` input passed into `Blockchain::push_history_sync`, and a malformed history list can violate these invariants and trigger a panic. `extend_history_sync` calls `this.history_store.add_to_history(..)` before comparing the computed history root against the macro block header (`block.history_root()`), so the panic can happen before later rejection checks run. The patch for this vulnerability is included as part of v1.3.0. No known workarounds are available.

Weakness: CWE-754 (Improper Check for Unusual or Exceptional Conditions), CWE-617 (Reachable Assertion), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-34066?

2 open source packages ship an affected version, including nimiq-blockchain. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nimiq-blockchain` | crates.io | All versions to 0.2.0 | None |
| `nimiq-blockchain` | crates.io | All versions to 0.2.0 | None |

Products: Nimiq Nimiq Proof-of-Stake.

## How do I fix CVE-2026-34066?

No fix has been published for CVE-2026-34066 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-34066 being exploited?

There is no known exploitation of CVE-2026-34066 in the wild and no public exploit code.

## Other vulnerabilities in nimiq-blockchain

- [CVE-2026-33471](https://insights.sbomify.com/CVE-2026-33471/): nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation (critical 9.6)
- [CVE-2026-40093](https://insights.sbomify.com/CVE-2026-40093/): nimiq-blockchain is missing a wall-clock upper bound on block timestamps (high 8.1)
- [CVE-2026-34063](https://insights.sbomify.com/CVE-2026-34063/): network-libp2p: Peer can crash the node by opening discovery protocol substream twice (high 7.5)
- [CVE-2026-34065](https://insights.sbomify.com/CVE-2026-34065/): nimiq-primitives: Node crash due to missing interlink validation in election macro block proposals (high 7.5)
- [CVE-2026-32605](https://insights.sbomify.com/CVE-2026-32605/): Nimiq: Remote crash via off-by-one signer bounds check in proposal buffer (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34066 and fix it if it is affected.

What it is: CVE-2026-34066 is a medium-severity denial of service vulnerability in nimiq-blockchain, published on 22 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-34066 in the wild and no public exploit code.

Affected packages and fixed versions:
- nimiq-blockchain (crates.io): affected all versions up to 0.2.0; no fix listed
- nimiq-blockchain (crates.io): affected all versions up to 0.2.0; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-34066/ (Markdown: https://insights.sbomify.com/CVE-2026-34066/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34066
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34066
- OSV: https://osv.dev/vulnerability/CVE-2026-34066

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34066/
Summaries are generated and may contain mistakes; the official description above is the record.