#VU71773 Incorrect Regular Expression in Prototype JavaScript Framework - CVE-2020-27511

Vulnerability identifier: #VU71773

Vulnerability risk: Low

CVSSv4.0: 2.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2020-27511

CWE-ID: CWE-185

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Prototype JavaScript Framework
Web applications / JS libraries

Vendor: Prototype Core Team

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient input validation in the stripTags and unescapeHTML components. A remote attacker can pass specially crafted data to the application and perform regular expression denial of service (ReDos) attack.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Prototype JavaScript Framework: 1.5.0 - 1.7.3

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External links
https://prototypejs.org/
https://github.com/yetingli/PoCs/blob/main/CVE-2020-27511/Prototype.md
https://github.com/prototypejs/prototype/blob/dee2f7d8611248abce81287e1be4156011953c90/src/prototype/lang/string.js#L283

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.