# CVE-2026-40164: jq: Algorithmic complexity DoS via hardcoded MurmurHash3 seed

> Attackers can cause CPU exhaustion in jq by submitting crafted JSON objects that exploit a hardcoded hash seed, leading to denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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:** Not needed
- **Fix available:** Yes
- **Published:** 13 Apr 2026
- **Updated:** 1 Sep 2026
- **Also known as:** ALPINE-CVE-2026-40164, AZL-82934, BELL-CVE-2026-40164, DEBIAN-CVE-2026-40164, ECHO-472e-db5d-af63, GHSA-wwj8-gxm6-jc29

## What is CVE-2026-40164?

CVE-2026-40164 is a high-severity denial of service vulnerability in jqlang jq, published on 13 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

jq is a command-line JSON processor. Before commit 0c7d133c3c7e37c00b6d46b658a02244fdd3c784, jq used MurmurHash3 with a hardcoded, publicly visible seed (0x432A9843) for all JSON object hash table operations, which allowed an attacker to precompute key collisions offline. By supplying a crafted JSON object (~100 KB) where all keys hashed to the same bucket, hash table lookups degraded from O(1) to O(n), turning any jq expression into an O(n²) operation and causing significant CPU exhaustion. This affected common jq use cases such as CI/CD pipelines, web services, and data processing scripts, and was far more practical to exploit than existing heap overflow issues since it required only a small payload. This issue has been patched in commit 0c7d133c3c7e37c00b6d46b658a02244fdd3c784.

Weakness: CWE-341 (Predictable from Observable State), CWE-407 (Inefficient Algorithmic Complexity), CWE-328 (Use of Weak Hash)

## Which versions are affected by CVE-2026-40164?


## How do I fix CVE-2026-40164?

Apply the vendor's patch.

## Is CVE-2026-40164 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40164 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40164 and fix it if it is affected.

What it is: CVE-2026-40164 is a high-severity denial of service vulnerability in jqlang jq, published on 13 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40164 exists.

Affected product: jqlang jq. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-40164/ (Markdown: https://insights.sbomify.com/CVE-2026-40164/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40164
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40164
- OSV: https://osv.dev/vulnerability/CVE-2026-40164

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-40164/
Summaries are generated and may contain mistakes; the official description above is the record.