CVE-2025-20777: 
NixOS vulnerability analysis and mitigation

CVE-2025-20777 is an out-of-bounds write vulnerability in the MediaTek display component affecting Android devices running versions 14.0, 15.0, and 16.0. It was published on December 2, 2025, and addressed in the MediaTek December 2025 Product Security Bulletin (Patch ID: ALPS10184870; Issue ID: MSV-4752). The vulnerability affects a wide range of MediaTek chipsets including MT6739, MT6761, MT6765, MT6768, MT6781, MT6789, MT6833, MT6835, MT6853, MT6855, MT6877, MT6878, MT6879, MT6883, MT6885, MT6886, MT6889, MT6893, MT6895, MT6897, MT6899, MT6983, MT6985, MT6989, MT6991, and numerous MT8xxx series chips. It carries a CVSS v3.1 base score of 6.7 (Medium) (MediaTek Bulletin, Red Hat CVE).

The vulnerability is classified as CWE-787 (Out-of-bounds Write) and stems from a missing bounds check in the display subsystem of MediaTek-powered Android devices. An attacker who has already obtained System-level privileges can exploit this flaw to write data beyond the bounds of an allocated memory buffer, potentially corrupting adjacent memory structures. The attack vector is local, requires high privileges (System-level), and no user interaction is needed. No public proof-of-concept or detailed technical write-up has been identified at this time (MediaTek Bulletin).

Successful exploitation could allow a local attacker with existing System privileges to further escalate privileges on the affected device, with high impact to confidentiality, integrity, and availability. The out-of-bounds write may enable unauthorized memory manipulation, potentially leading to arbitrary code execution at a higher privilege level or system instability. Given the requirement for pre-existing System-level access, the practical blast radius is somewhat constrained, but the vulnerability remains significant in chained attack scenarios (MediaTek Bulletin, Red Hat CVE).

There is no evidence of active in-the-wild exploitation or a publicly available proof-of-concept for CVE-2025-20777. The EPSS score is approximately 0.018% (0.000180), indicating a very low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Exploitation requires the attacker to already possess System-level privileges on the target device, significantly limiting the attack surface (MediaTek Bulletin).

MediaTek has released a patch (Patch ID: ALPS10184870) addressed in the December 2025 MediaTek Product Security Bulletin. Users and device manufacturers should apply the latest security updates for Android 14.0, 15.0, and 16.0 on affected MediaTek chipsets. Lenovo has also issued a corresponding advisory for affected MediaTek-based tablets (MediaTek Bulletin, Lenovo Advisory). As a general mitigation, organizations should strictly limit and audit System-level access on Android devices and monitor for unauthorized privilege escalation activity.