CVE-2025-20741 is a heap overflow vulnerability classified under CWE-122, affecting the WLAN AP driver in multiple MediaTek chipsets including MT6890, MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, and MT7986. The root cause is an incorrect bounds check in the driver code that allows an out-of-bounds write to heap memory. This vulnerability can be exploited by an attacker who already has local system privileges, enabling them to escalate their privileges further, potentially gaining higher system-level control. No user interaction is required for exploitation, which increases the risk in environments where local access is possible. The affected software versions include SDK release 7.6.7.2 and earlier, as well as openWRT versions 19.07 and 21.02, which are commonly used in embedded devices such as wireless routers and access points. Although no public exploits have been reported, the vulnerability's presence in widely deployed chipsets means it could be targeted in the future. The lack of a CVSS score necessitates an assessment based on the vulnerability's characteristics: it impacts confidentiality and integrity by enabling privilege escalation, has a medium to high impact on availability if exploited to disrupt device operation, and requires local system privileges but no user interaction. The vulnerability was publicly disclosed in November 2025, with MediaTek assigning the issue ID MSV-3958 and patch ID WCNCR00434422, though no patch links are currently provided. Organizations using affected devices should monitor for vendor patches and apply them promptly to mitigate risk.

For European organizations, this vulnerability poses a significant risk primarily in environments where MediaTek-based wireless access points or routers are deployed, especially those running affected SDK or openWRT versions. Exploitation could allow malicious insiders or attackers with limited local access to escalate privileges, potentially leading to unauthorized configuration changes, interception or manipulation of network traffic, or disruption of wireless network services. This could compromise the confidentiality and integrity of sensitive communications and impact availability of network infrastructure. Critical sectors such as telecommunications, government, finance, and industrial control systems that rely on these devices for secure wireless connectivity could be particularly affected. The lack of user interaction requirement increases the threat in shared or multi-tenant environments. Additionally, the vulnerability could be leveraged as a stepping stone for further lateral movement within corporate networks. The absence of known exploits currently reduces immediate risk but does not eliminate the potential for future targeted attacks.

1. Immediately inventory all network devices to identify those using affected MediaTek chipsets and SDK/openWRT versions. 2. Restrict local access to devices to trusted personnel only, employing strong physical and logical access controls. 3. Monitor vendor communications closely for official patches or firmware updates addressing CVE-2025-20741 and apply them as soon as they become available. 4. Where patching is delayed, consider isolating vulnerable devices on segmented networks to limit exposure. 5. Implement enhanced logging and monitoring on affected devices to detect unusual privilege escalation attempts or anomalous behavior. 6. Employ network-level security controls such as NAC (Network Access Control) to prevent unauthorized devices or users from gaining local access. 7. For openWRT users, consider upgrading to newer, unaffected versions or alternative firmware if patches are unavailable. 8. Conduct regular security audits and penetration tests focusing on wireless infrastructure to identify and remediate potential exploitation paths. 9. Educate IT and security teams about the vulnerability specifics to ensure rapid response capability. 10. Maintain an incident response plan that includes scenarios involving local privilege escalation on network infrastructure devices.