# CVE-2026-53970: ZeroBrew version 0.3.1 and prior Missing Checksum Verification RCE via shim.rb

> Attackers can execute arbitrary code by substituting malicious content in package downloads due to missing checksum verification in ZeroBrew.

- **Severity:** High 7.5 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **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:** 14 Aug 2026
- **Updated:** 18 Aug 2026
- **Also known as:** GHSA-9pp6-v7j8-j65j

## What is CVE-2026-53970?

CVE-2026-53970 is a high-severity vulnerability in lucasgelfond ZeroBrew, published on 14 Aug 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

ZeroBrew version 0.3.1 and prior contains a missing integrity verification vulnerability in the Ruby compatibility shim that allows network attackers to execute arbitrary code by substituting malicious content at formula resource or URL-based patch URLs without checksum validation. Attackers can intercept or replace downloads for secondary resource and patch paths in shim.rb, injecting attacker-controlled build steps or source tree modifications that execute during source builds via 'zb install --build-from-source' without any integrity warning.

Weakness: CWE-494 (Download of Code Without Integrity Check)

## Which versions are affected by CVE-2026-53970?


## How do I fix CVE-2026-53970?

No fix has been published for CVE-2026-53970 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-53970 being exploited?

There is no known exploitation of CVE-2026-53970 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53970 and fix it if it is affected.

What it is: CVE-2026-53970 is a high-severity vulnerability in lucasgelfond ZeroBrew, published on 14 Aug 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-2026-53970 in the wild and no public exploit code.

Affected product: lucasgelfond ZeroBrew. 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-2026-53970/ (Markdown: https://insights.sbomify.com/CVE-2026-53970/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53970
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53970
- OSV: https://osv.dev/vulnerability/CVE-2026-53970

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53970/
Summaries are generated and may contain mistakes; the official description above is the record.