ASUS began rolling out firmware WW-35.0604.0404.165 for Zenfone 10 on September 1. The update applies to WW, EU and JP SKUs and is also available as a 4.19GB full software image through ASUS support.

The over-the-air rollout happens in batches, so availability can vary between devices for several days.

Android 15 stays, while security moves forward

This is not an Android 16 upgrade. Zenfone 10 remains on Android 15, with ASUS adding the August 5, 2026 Android security patch and listing general system-stability optimization.

That makes for a very small changelog. There is no major interface redesign or new headline feature attached to the release.

On a three-year-old phone, regular vulnerability fixes are arguably the more useful update anyway.

Downgrading is no longer an option

The unusual part of the release note is ASUS's warning that users will not be able to downgrade to previous software after installing this firmware.

The company frames the restriction as a security measure. Preventing rollback can stop a device from being deliberately returned to older firmware containing vulnerabilities that have already been patched.

Most owners may never notice the change. Enthusiasts who deliberately keep older firmware, troubleshoot updates or value the ability to roll back will have fewer options.

There still is not much else like the Zenfone 10

The continued support stands out partly because ASUS never produced a straightforward replacement for the Zenfone 10's compact format.

Its 5.9-inch AMOLED display and 172-gram body remain unusually small by modern flagship standards. Hardware includes Snapdragon 8 Gen 2, up to 16GB of LPDDR5X memory, UFS 4.0 storage and a 4,300mAh battery.

The display can reach 144Hz in supported gaming scenarios through Game Genie, and the phone also includes Qi wireless charging.

Those specifications no longer describe a 2026 flagship, but the combination of genuinely compact dimensions and high-end hardware has become harder to find rather than easier.

Security support is scheduled through 2027

ASUS's official support policy lists Zenfone 10 for security updates through 2027. The phone was promised two operating-system upgrades, taking it from the Android 13 software it launched with to Android 15.

That policy is considerably shorter than the long support windows now offered on several newer premium Android phones.

Still, the September 2026 firmware shows that the compact Zenfone has not been quietly abandoned yet. For an old 5.9-inch phone, a boring security update is a perfectly respectable way to stay alive.