CVE-2017-16030
ReDoS via long UserAgent header in useragent
Useragent is used to parse useragent headers. It uses several regular expressions to accomplish this. An attacker could edit their own headers, creating an arbitrarily long useragent string, causing the event loop and server to block. This affects Useragent 2.1.12 and earlier.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
Useragent is used to parse useragent headers. It uses several regular expressions to accomplish this. An attacker could edit their own headers, creating an arbitrarily long useragent string, causing the event loop and server to block. This affects Useragent 2.1.12 and earlier.
- Record
CVE-2017-16030- CVSS 3.0
- 7.5 High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:N/I:N/A:P - Weakness
- CWE-400
- Updated
- 2026-11-02
CVE List No score
Useragent is used to parse useragent headers. It uses several regular expressions to accomplish this. An attacker could edit their own headers, creating an arbitrarily long useragent string, causing the event loop and server to block. This affects Useragent 2.1.12 and earlier.
- Record
CVE-2017-16030- Weakness
- CWE-400
- Updated
- 2026-11-02
EUVDEUVD-2018-0302 No score
Useragent is used to parse useragent headers. It uses several regular expressions to accomplish this. An attacker could edit their own headers, creating an arbitrarily long useragent string, causing the event loop and server to block. This affects Useragent 2.1.12 and earlier.
- Record
EUVD-2018-0302- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-pjmx-9xr3-82qr No score
ReDoS via long UserAgent header in useragent
Affected versions of useragent are vulnerable to regular expression denial of service when an arbitrarily long User-Agent header is parsed.
Proof of Concept
var useragent = require('useragent');
var badUserAgent = 'MSIE 0.0'+Array(900000).join('0')+'XBLWP';
var request = 'GET / HTTP/1.1\r\nUser-Agent: ' + badUserAgent + '\r\n\r\n';
console.log(useragent.parse(request));
Recommendation
Update to version 2.1.13 or later.
- Record
GHSA-pjmx-9xr3-82qr- Weakness
- CWE-400
- Updated
- 2026-11-02
OSVGHSA-pjmx-9xr3-82qr No score
ReDoS via long UserAgent header in useragent
Affected versions of useragent are vulnerable to regular expression denial of service when an arbitrarily long User-Agent header is parsed.
Proof of Concept
var useragent = require('useragent');
var badUserAgent = 'MSIE 0.0'+Array(900000).join('0')+'XBLWP';
var request = 'GET / HTTP/1.1\r\nUser-Agent: ' + badUserAgent + '\r\n\r\n';
console.log(useragent.parse(request));
Recommendation
Update to version 2.1.13 or later.
- Record
GHSA-pjmx-9xr3-82qr- Weakness
- CWE-400
- Updated
- 2026-11-02
Affected products
Affected packages
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2017-16030 is a high vulnerability (CVSS 7.5) in Useragent Project Useragent, published June 4, 2018. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.14%, the 66th percentile. Fixed in useragent 2.1.13.