CVE-2018-9428 is a high severity out-of-bounds write that follows a use-after-free in the AAudio service (startDevice in AAudioServiceStreamBase.cpp). NVD scores it 7.8. Google fixes it at security patch level 2018-07-01 or later. Install the device update that reaches that level.
What's affected
- Product: Android, in the AAudio service (startDevice in AAudioServiceStreamBase.cpp).
- Releases listed by the bulletin: 8.1. The NVD product list shows only some Android releases, so treat the bulletin as the fuller list.
- Fixed in: security patch level 2018-07-01 or later, according to the Android Security Bulletin for July 2018.
- Impact in the record: local arbitrary code execution with no extra privileges, user interaction needed.
- Severity: NVD scores it 7.8 High (vector AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H). The bulletin lists it as High, type EoP. The two ratings agree.
- Weakness classes: CWE-416 (Use After Free), CWE-787 (Out-of-bounds Write).
How to check if you're exposed
- On the device, open Settings and find the Android security patch level, usually under About phone. The exact path varies by manufacturer. A date earlier than 2018-07-01 means the fix is not present.
- With a USB debugging connection, run
adb shell getprop ro.build.version.security_patch. It prints the patch level as a date. You need 2018-07-01 or later. - For a fleet, export the patch level from your mobile device management console and filter for dates earlier than 2018-07-01.
- Match each device against the release list above. Devices on releases outside it are not named for this CVE, but check them against the other entries in the same bulletin.
What to do now
- Identify every Android device in scope and record its current security patch level.
- Roll out the manufacturer or carrier update that reaches 2018-07-01 or later. Google publishes the fixes, but each device maker decides when its devices receive them.
- For devices that no longer receive updates, plan replacement or limit what they can reach, such as corporate mail and internal apps.
- Write the update policy down, with a maximum patch age, and report exceptions.
Why it matters
Android 8.1 is the only release listed. The record scores 7.8 with local access and user interaction required (AV:L/UI:R). A user has to take some action, such as opening an app, before the weakness can be reached.
A use-after-free means the code keeps using an object after it has been released. When the memory is reused, the stale pointer reads or writes data that belongs to something else. Here the end result is an out-of-bounds write inside the audio service process. The record's KEV flag is false, so CISA does not list it as exploited. The bulletin says Google had no reports of active customer exploitation or abuse of the newly reported issues in it. That is the absence of a report in the sources read, not proof that no one has tried.
Quick check
Why is the bulletin type EoP when the record says code execution?
The bulletin sorts every issue into a short category list, and EoP is the category it used. The NVD description says local arbitrary code execution. Both describe the same capability from different angles.
Which patch level should I look for?
The Android Security Bulletin for July 2018 places this fix at 2018-07-01. Any date at or after 2018-07-01 includes it. Some makers ship it under a different update name, so check the date.
Sources
- Android Security Bulletin for July 2018: Affected releases, severity, type and the patch level that carries the fix.
Last reviewed: 19 October 2026.
