GHSA-qhp6-635j-x7r2

ghsaUSosv

Static Web Server affected by timing-based username enumeration in Basic Authentication due to early response on invalid usernames

view advisory published 2026-02-20Licence: CC-BY-4.0

## 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: | User Type | Average Response Time | | :--- | :--- | | **Invalid User** | 0.409861 ms | | **Valid User** | 0.250925 ms | | **Difference** | **~0.158936 ms** | 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.

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describes (1)

Related CVEs.

IDseverity exploitable
CVE-2026-27480US——
Static Web Server (SWS) is a production-ready web server suitable for static web files or assets. In versions 2.1.0 through 2.40.1, a timing-based username enumeration vulnerabilit…
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