# CVE-2026-27480: static-web-server — Fixed in 2.41.0

🦀

🦀 crates.io

Not in CISA KEV

MEDIUM severity

# CVE-2026-27480 — static-web-server

MEDIUM [Fix: static-web-server/static-web-server@7bf0fd4](https://github.com/static-web-server/static-web-server/commit/7bf0fd425eb10dac9bf9ef5febce12c4dd039ce1)

CVE-2026-27480 is a medium-severity (CVSS 5.3) CWE-204 vulnerability in static-web-server. A fix is available for static-web-server — see the affected versions and patch details below.

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

Also known as[GHSA-qhp6-635j-x7r2](/vulnerability/GHSA-qhp6-635j-x7r2)

Published

Feb 21, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### Proof-of-concept exploit code exists

-   CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
-   CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-27480.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs34th percentile — riskier than 34% of all scored CVEsHighest risk

0.00%0.31%0.62%0.93%0.0%0.4%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## How urgent is this, really

## Where this sits among everything scored

## Real-World Exposure

1 pkg affected

🦀`static-web-server`

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.

## 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.

## Affected Packages

1 total 1 fixed

Ecosystem

Package

Vulnerable range

Fix

🦀crates.io

`static-web-server` 

≥ 2.1.0&&< 2.41.0

2.41.0`cargo update -p static-web-server --precise 2.41.0`

## Affected Products

1 product · 1 configurations

Application

`static web server`static-web-server

≥ 2.1.0 && < 2.41.0

range

## Detection & mitigation playbook

Open-source dependency

1.  ### Detect
    
    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for static-web-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
    
2.  ### Fix
    
    Update static-web-server to 2.41.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27480 is resolved across your whole dependency graph.
    
3.  ### Workarounds
    
    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
    

## Frequently Asked Questions

\## 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 discrepanc

O3 Security · Impact-Aware SCA

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