CVE-2026-27480: Static Web Server: Timing-Based Username Enumeration in Basic Authentication

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-02-21 · updated 2026-06-17
Weakness: CWE-204

Description

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 vulnerability in Basic Authentication allows attackers to identify valid users by exploiting early responses for invalid usernames, enabling targeted brute-force or credential-stuffing attacks. SWS checks whether a username exists before verifying the password, causing valid usernames to follow a slower code path (e.g., bcrypt hashing) while invalid usernames receive an immediate 401 response. This timing discrepancy allows attackers to enumerate valid accounts by measuring response-time differences. This issue has been fixed in version 2.41.0.

Affected products

static-web-server: from 2.1.0 before 2.41.0 — fixed in 2.41.0

How to fix

Upgrade to a fixed version: static-web-server 2.41.0. Check the vendor advisory for mitigations.

References

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