CVE-2018-20164: An issue was discovered in regex.yaml (aka regexes.yaml) in UA-Parser UAP-Core before 0.6.0

Q: How do I fix CVE-2018-20164?

user agent parser-core: upgrade to 0.6.0. Exact commands for each OS are on this page.

Q: Is CVE-2018-20164 being exploited?

CVE-2018-20164 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2018-20164 affect?

CVE-2018-20164 affects user agent parser-core. Severity is medium (CVSS 5.3). An issue was discovered in regex.yaml (aka regexes.yaml) in UA-Parser UAP-Core before 0.6.0. A Regular Expression Denial of Service (ReDoS) issue allows remote attackers to overload a server by setting the User-Agent header in an HTTP(S) re

Q: How urgent is CVE-2018-20164?

Priority 51/100. Public exploit reference; Remotely exploitable, no login, no user action

This week

MEDIUM 5.3REMOTEUPGRADE

CVE-2018-20164 is a medium-severity flaw (CVSS 5.3) affecting user agent parser-core. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in regex.yaml (aka regexes.yaml) in UA-Parser UAP-Core before 0.6.0. A Regular Expression Denial of Service (ReDoS) issue allows remote attackers to overload a server by setting the User-Agent header in an HTTP(S) request to a value containing a long digit string. (The UAP-Core project contains the vulnerability, propagating to all implementations.)

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.3% (top 12%)
CISA exploited list	No
Weakness	CWE-185
Published	2019-02-13
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: uaparser

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2019-02-13 14:29 UTCPublished CVE record published
2026-06-17 01:52 UTCUpdated Record last modified

uaparser user agent parser-core UPGRADE

Affected: < 0.6.0

Fixed in: 0.6.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy user-agent-parser-core || rpm -q user-agent-parser-core || user-agent-parser-core --version

2. UPGRADE to 0.6.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade user-agent-parser-core

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade user-agent-parser-core

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2018-20164?

user agent parser-core: upgrade to 0.6.0. Exact commands for each OS are on this page.

Is CVE-2018-20164 being exploited?

CVE-2018-20164 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2018-20164 affect?

CVE-2018-20164 affects user agent parser-core. Severity is medium (CVSS 5.3). An issue was discovered in regex.yaml (aka regexes.yaml) in UA-Parser UAP-Core before 0.6.0. A Regular Expression Denial of Service (ReDoS) issue allows remote attackers to overload a server by setting the User-Agent header in an HTTP(S) re

How urgent is CVE-2018-20164?

Priority 51/100. Public exploit reference; Remotely exploitable, no login, no user action

References

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