Username enumeration via early authentication rejection
Published Feb 21, 2026 · Updated Feb 21, 2026
Timing-based username enumeration in Static Web Server 2.1.0 through 2.40.1 allows remote attackers to identify valid Basic Authentication users. Basic Authentication's check_request function in src/basic_auth.rs returns 401 before bcrypt verification when the supplied username differs, while valid usernames incur password hashing. Basic Authentication must be enabled and reachable; the resulting account list supports targeted password guessing but does not disclose passwords or grant access by itself.
Summary
What happened
Timing-based username enumeration in Static Web Server 2.1.0 through 2.40.1 allows remote attackers to identify valid Basic Authentication users. Basic Authentication's check_request function in src/basic_auth.rs returns 401 before bcrypt verification when the supplied username differs, while valid usernames incur password hashing. Basic Authentication must be enabled and reachable; the resulting account list supports targeted password guessing but does not disclose passwords or grant access by itself.
The record
- CVE
- CVE-2026-27480
- Published
- Feb 21, 2026
- Updated
- Feb 21, 2026
- Vendor
- Static Web Server
- Product
- Static Web Server
- Classifications
- CWE-204, T1589.001
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 21, 2026CVE publishedPublication date reported by the CVE source.
- Feb 21, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=>= 2.1.0, < 2.41.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Basic Authentication response-timing proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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