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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

EPSS

• CVE-2026-27480: 0.39% estimated exploitation activity in the next 30 days; percentile 33.60 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

20 Feb 2026, 18:25 UTC

Last modified by the source

23 Feb 2026, 22:28 UTC

Source last checked

26 Oct 2026, 15:39 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-qhp6-635j-x7r2

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# Patch Next advisory brief: CVE-2026-27480

Advisory: Static Web Server affected by timing-based username enumeration in Basic Authentication due to early response on invalid usernames
IDs: CVE-2026-27480, GHSA-qhp6-635j-x7r2
Record: https://patchnext.com/advisories/cve-2026-27480 (revision 1, source checked 26 Oct 2026, 15:39 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: static-web-server 2.41.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io static-web-server: affected >= 2.1.0, < 2.41.0; fixed in 2.41.0

## Suggested inspection (read-only)
- crates.io static-web-server: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on static-web-server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-qhp6-635j-x7r2 (GitHub-reviewed advisory GHSA-qhp6-635j-x7r2 lists affected ranges: crates.io static-web-server >=2.1.0 <2.41.0)

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