#VU57848 Input validation error in Unicode - CVE-2021-42574

Vulnerability identifier: #VU57848

Vulnerability risk: Low

CVSSv4.0: 1.1 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/U:Clear]

CVE-ID: CVE-2021-42574

CWE-ID: CWE-20

Exploitation vector: Local

Exploit availability: Yes

Vulnerable software:
Unicode
Universal components / Libraries / Libraries used by multiple products

Vendor: Unicode inc.

Description

The vulnerability allows an attacker to bypass certain security checks.

The vulnerability exists in the Bidirectional Algorithm in the Unicode Specification. It permits the visual reordering of characters via control sequences, which can be used to craft source code that renders different logic than the logical ordering of tokens ingested by compilers and interpreters.

An attacker can leverage this behavior to encode source code for compilers accepting Unicode such that targeted vulnerabilities are introduced invisibly to human reviewers.

Mitigation
Cybersecurity Help is currently unaware of any official solution to address this vulnerability.

Vulnerable software versions

Unicode: 4.1.0 - 14.0.0

---

External links
https://www.openwall.com/lists/oss-security/2021/11/01/1
https://www.openwall.com/lists/oss-security/2021/11/01/4
https://www.openwall.com/lists/oss-security/2021/11/01/5
https://www.openwall.com/lists/oss-security/2021/11/01/6
https://github.blog/changelog/2021-10-31-warning-about-bidirectional-unicode-text/

---

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.