CVE-2021-25255 is a high-severity vulnerability identified in Yandex Browser Lite for Android versions prior to 21.1.0. The underlying issue is classified as CWE-20, which refers to improper input validation. This vulnerability allows remote attackers to cause a denial of service (DoS) condition in the affected browser. Specifically, the browser fails to properly validate certain inputs, which can be crafted by an attacker to trigger a crash or otherwise disrupt normal operation. The vulnerability does not require any privileges or authentication to exploit, and user interaction is necessary, such as visiting a maliciously crafted webpage or clicking a link. The CVSS v4.0 base score is 8.3, indicating a high severity level. The attack vector is network-based (AV:N), with low attack complexity (AC:L), no privileges required (PR:N), and no user authentication needed (AT:N). However, user interaction is required (UI:P). The impact is primarily on availability, as the vulnerability leads to denial of service, potentially causing the browser to crash or become unresponsive. There is no indication of confidentiality or integrity compromise. No known exploits are currently reported in the wild, and no official patches or mitigation links are provided in the data, though the fixed version is 21.1.0. The vulnerability affects the Android platform specifically, targeting users of Yandex Browser Lite, a lightweight version of the Yandex browser designed for resource-constrained devices or users with limited bandwidth. The improper input validation could be triggered by maliciously crafted web content or URLs, making it a risk for users who browse untrusted or malicious websites.

For European organizations, the primary impact of this vulnerability is the potential disruption of user productivity and service availability for employees or customers using Yandex Browser Lite on Android devices. While the vulnerability does not directly compromise sensitive data confidentiality or integrity, denial of service conditions can lead to operational interruptions, especially in environments where Yandex Browser Lite is used for accessing web-based applications or services. This could be particularly relevant for organizations with mobile workforces or those in sectors relying on Android devices for field operations. Additionally, if exploited at scale, it could be used as part of a broader denial of service campaign targeting users in Europe, potentially affecting business continuity. The lack of known exploits in the wild reduces immediate risk, but the high CVSS score and ease of exploitation without privileges mean that organizations should treat this vulnerability seriously. Since Yandex products have a significant user base in Russia and some Eastern European countries, organizations in these regions may see higher exposure. However, the browser's usage in Western Europe is less widespread, potentially limiting impact there. Still, any European organization with users who have installed Yandex Browser Lite should be aware of this risk.

1. Update to Yandex Browser Lite version 21.1.0 or later, as this version addresses the vulnerability. 2. Implement mobile device management (MDM) policies to enforce browser updates and restrict installation of outdated or unapproved applications. 3. Educate users about the risks of visiting untrusted websites and clicking on suspicious links, as user interaction is required for exploitation. 4. Monitor network traffic for unusual patterns that could indicate attempts to exploit this vulnerability, such as repeated crashes or abnormal browser behavior. 5. Consider deploying endpoint protection solutions capable of detecting and mitigating denial of service attempts on mobile devices. 6. For organizations with critical mobile operations, evaluate alternative browsers with stronger security postures and better update management. 7. Coordinate with IT and security teams to ensure rapid patch deployment and incident response readiness in case exploitation attempts are detected.