CVE-2021-21317

uap-core in an open-source npm package which contains the core of BrowserScopes 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.

Weakness

The product does not properly control the allocation and maintenance of a limited resource.

Affected Software

Potential Mitigations

• Mitigation of resource exhaustion attacks requires that the target system either:

• The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.

• The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/147.html
• https://cwe.mitre.org/data/definitions/227.html
• https://cwe.mitre.org/data/definitions/492.html

References

• https://github.com/ua-parser/uap-core/commit/dc9925d458214cfe87b93e35346980612f6ae96c
• https://github.com/ua-parser/uap-core/security/advisories/GHSA-p4pj-mg4r-x6v4
• https://www.npmjs.com/package/uap-core
• https://github.com/ua-parser/uap-core/commit/dc9925d458214cfe87b93e35346980612f6ae96c
• https://github.com/ua-parser/uap-core/security/advisories/GHSA-p4pj-mg4r-x6v4
• https://www.npmjs.com/package/uap-core