CVE-2021-21317: Denial of Service in uap-core

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-02-16 · updated 2026-06-17
Weakness: CWE-400

Description

uap-core in an open-source npm package which contains the core of BrowserScope's original user agent string parser. In uap-core before version 0.11.0, some regexes are vulnerable to regular expression denial of service (REDoS) due to overlapping capture groups. This allows remote attackers to overload a server by setting the User-Agent header in an HTTP(S) request to maliciously crafted long strings. This is fixed in version 0.11.0. Downstream packages such as uap-python, uap-ruby etc which depend upon uap-core follow different version schemes.

Affected products

ua-parser uap-core: before 0.11.0 — fixed in 0.11.0

How to fix

Upgrade to a fixed version: ua-parser uap-core 0.11.0. Check the vendor advisory for mitigations.

References

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