CVE-2019-2215

What Is the Android Binder Driver?

Binder is the core inter-process communication (IPC) mechanism in Android, implemented as a kernel driver (binder.c) that lets apps and system services exchange objects and invoke methods across process boundaries. Because Binder is used constantly by every app and by privileged system services, a memory-corruption bug in the Binder driver is reachable from ordinary, unprivileged app code and can be leveraged to escalate straight into the Linux kernel — the most privileged layer on the device.

Overview

CVE-2019-2215 is a use-after-free vulnerability in the Android kernel's Binder driver that allows a malicious local application to escalate privileges and execute code in the kernel context, effectively rooting the device. It is notable both for its severity and for the fact that it was discovered because it was already being actively exploited as a zero-day, not through routine fuzzing or code review.

Technical Details

The bug (CWE-416, Use-After-Free) occurs in Binder's handling of certain reference-counted objects: under a specific sequence of operations, the driver frees an object while a stale reference to it is still retained and later dereferenced, giving an attacker the ability to control freed kernel memory. A local, unprivileged app can trigger the free/use sequence and, with a heap-grooming technique, turn the use-after-free into arbitrary kernel memory read/write, and from there full code execution with kernel privileges. Notably, this exact class of bug had been reported and fixed once before (in late 2017/2018 Android kernels via a related upstream Binder fix) but a subsequent kernel refactor reintroduced the vulnerable pattern — a case of a fixed bug resurfacing.

Discovery

CVE-2019-2215 was discovered by Maddie Stone of Google's Project Zero team, who found evidence that the bug was being actively exploited in the wild rather than discovering it proactively. Google's analysis, along with reporting at the time, linked the exploit to NSO Group, the Israeli surveillance vendor behind the Pegasus spyware platform, which was observed using this kernel bug as part of an Android privilege-escalation chain.

Exploitation Context

This vulnerability was exploited as a zero-day against specific targeted individuals before a patch was available, consistent with commercial spyware tooling rather than broad opportunistic attack. It affected a wide range of Android devices, including popular models from Pixel, Samsung, Huawei, Xiaomi, and others, depending on kernel version. Well after the original disclosure, security researchers also documented this vulnerability being reused — chained with other privilege-escalation bugs — in later malware campaigns targeting outdated, unpatched Android devices, underscoring how long-lived Android kernel bugs remain valuable to attackers given slow OEM patch rollout across the device ecosystem.

Remediation

1. Apply the Android Security Bulletin patch (October 2019 and later) appropriate for the device's kernel version and OEM.
2. Update to a supported Android version — devices no longer receiving security patches from the OEM should be considered permanently at risk from this and similar kernel bugs.
3. Avoid installing apps from untrusted sources, since local code execution is the prerequisite for triggering this vulnerability.
4. Use mobile threat defense / EDR tooling capable of detecting kernel exploitation indicators on high-risk or high-value user devices.
5. Prioritize patching for high-risk individuals (journalists, activists, executives, government officials) given this bug's documented use in targeted surveillance operations.