CVE-2026-27480
Static Web Server affected by timing-based username enumeration in Basic Authentication due to early response on invalid usernames
Description
## 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.
How to fix CVE-2026-27480
To remediate CVE-2026-27480, upgrade the affected package to a fixed version below.
- —upgrade to 2.41.0 or later
Is CVE-2026-27480 being exploited?
Low — EPSS is 0.3%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- >= 2.1.0, < 2.41.0