Byass due to validation before canonicalization in serve
Versions of serve before 6.5.2 are vulnerable to the bypass of the ignore functionality. The bypass is possible because validation happens before canonicalization of paths and filenames.
Example: Here we have a server that ignores the file test.txt.
const serve = require('serve')
const server = serve(__dirname, {
port: 1337,
ignore: ['test.txt']
})Using the URL encoded form of a letter (%65 instead of e) attacker can bypass the ignore control accessing the file.
curl http://localhost:1337/t%65st.txt
Additionally this technique can be used to get directory listings of ignored directories.
Recommendation
Update to version 6.5.2 or later.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | serve | < 6.5.2 | 6.5.2 |
References
- Weakness (CWE)
-- Platform
- npm
- Package
serve- Disclosed
- 01.09.2020
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-wm7q-rxch-43mx - CC BY 4.0
Vulnerability history: serve
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 9
- First → latest
- 07.2018 08.2021
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 5
- Medium 4
Disclosures per year
- 2018: 2
- 2019: 2
- 2020: 4
- 2021: 1
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 0
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