Inefficient Regular Expression Complexity in koa
Summary
Koa uses an evil regex to parse the X-Forwarded-Proto and X-Forwarded-Host HTTP headers. This can be exploited to carry out a Denial-of-Service attack.
PoC
Coming soon.
Impact
This is a Regex Denial-of-Service attack and causes memory exhaustion. The regex should be improved and empty values should not be allowed.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | koa | >= 2.0.0, < 2.15.4, >= 3.0.0-alpha.0, < 3.0.0-alpha.3, >= 1.0.0, < 1.7.1, < 0.21.2 | 2.15.4, 3.0.0-alpha.3, 1.7.1, 0.21.2 |
References
- https://github.com/koajs/koa/security/advisories/GHSA-593f-38f6-jp5m
- https://nvd.nist.gov/vuln/detail/CVE-2025-25200
- https://github.com/koajs/koa/commit/5054af6e31ffd451a4151a1fe144cef6e5d0d83c
- https://github.com/koajs/koa/commit/5f294bb1c7c8d9c61904378d250439a321bffd32
- https://github.com/koajs/koa/commit/93fe903fc966635a991bcf890cfc3427d33a1a08
- https://github.com/koajs/koa
- https://github.com/koajs/koa/releases/tag/2.15.4
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H- Weakness (CWE)
CWE-1333- Platform
- npm
- Package
koa- Disclosed
- 12.02.2025
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-593f-38f6-jp5m - CC BY 4.0
Vulnerability history: koa
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
- 5
- First → latest
- 02.2025 02.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 1
- Medium 2
- Low 1
Disclosures per year
- 2025: 4
- 2026: 1
-
Inefficient Regular Expression Complexity in koa this entry
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