Summary

A Timing-based username enumeration in Basic Authentication vulnerability due to early response on invalid usernames could allow attackers to identify valid users and focus their efforts on targeted brute-force or credential-stuffing attacks.

Details

SWS validates the provided username before performing any password verification.

• Invalid Username: The server returns a 401 Unauthorized response immediately.
• Valid Username: The server proceeds to verify the password (e.g., using bcrypt), which introduces a different execution path and measurable timing discrepancy.

This allows an attacker to distinguish between existing and non-existing accounts by analyzing response times.

PoC

The following statistical results were obtained by measuring the mean response time over 100 iterations using a custom Rust script:

While the valid user responded faster in this specific test environment, the statistically significant gap confirms that the authentication logic does not execute in constant time.

Impact

Users using the SWS' Basic Authentication feature are primarily impacted.

References

• GHSA-qhp6-635j-x7r2
• static-web-server/static-web-server@7bf0fd4
• https://nvd.nist.gov/vuln/detail/CVE-2026-27480