CVE-2025-20741 is a heap overflow vulnerability identified in the WLAN Access Point (AP) driver of multiple MediaTek chipsets, specifically 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 type of vulnerability is classified under CWE-122 (Heap-based Buffer Overflow). The flaw can be exploited locally by an attacker who already possesses System-level privileges on the device, meaning the attacker must have significant access before leveraging this vulnerability. No user interaction is required to trigger the overflow, which can lead to escalation of privileges, potentially allowing the attacker to execute arbitrary code with elevated rights, corrupt memory, or cause denial of service. The affected software versions include MediaTek SDK release 7.6.7.2 and earlier, as well as openWRT versions 19.07 and 21.02 that incorporate these drivers. The vulnerability was published on November 4, 2025, with a CVSS v3.1 base score of 6.7, indicating a medium severity level. The vector metrics (AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H) show that the attack requires local access and high privileges but can severely impact confidentiality, integrity, and availability. No public exploits have been reported yet, but the presence of this vulnerability in widely used wireless chipsets embedded in routers and IoT devices poses a notable risk. MediaTek has assigned a patch ID (WCNCR00434422) for remediation, though no direct patch links are provided in the data.

The primary impact of CVE-2025-20741 is local privilege escalation on devices using the affected MediaTek chipsets. An attacker with existing System privileges can exploit the heap overflow to gain higher privileges or execute arbitrary code, potentially compromising the device's confidentiality, integrity, and availability. This could lead to unauthorized access to sensitive data, persistent malware installation, or disruption of wireless network services. Since these chipsets are commonly embedded in wireless routers, IoT devices, and network infrastructure, exploitation could affect enterprise networks, service providers, and consumer environments. The vulnerability could be leveraged as part of a multi-stage attack to deepen system compromise or pivot to other network segments. The lack of required user interaction facilitates stealthy exploitation once local access is obtained. Although no known exploits are currently active, the widespread deployment of affected chipsets means the potential attack surface is large, especially in environments running vulnerable SDK or openWRT versions. The medium severity rating reflects the need for timely mitigation to prevent escalation from already compromised accounts.

Organizations should immediately inventory devices using the affected MediaTek chipsets (MT6890, MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, MT7986) and verify the firmware or SDK versions in use. Upgrading to versions beyond SDK release 7.6.7.2 or openWRT versions later than 21.02, once patches are released, is critical. Until patches are available, restrict local access to trusted administrators only and implement strict access controls to prevent attackers from obtaining System privileges. Employ network segmentation to isolate vulnerable devices and monitor for unusual local privilege escalation attempts. Use host-based intrusion detection systems (HIDS) to detect anomalous behavior indicative of heap overflow exploitation. Vendors and integrators should prioritize releasing firmware updates incorporating the patch ID WCNCR00434422. Additionally, conduct regular security audits of wireless infrastructure and consider disabling or limiting WLAN AP driver features if feasible. Document and enforce strong endpoint security policies to reduce the risk of initial compromise that could lead to exploitation of this vulnerability.