Galaxy S25 Ultra and Galaxy S24 Ultra owners woke up in July 2026 to find their $1,299.99 flagships losing charge faster than a budget phone — not because the hardware failed, but because Samsung's July security patch appears to have kicked off a stuck background process that never stops running. Battery levels that used to last a full day are now collapsing within hours. Samsung has not said a word publicly about any of it.

The specific numbers, documented in real time across Samsung's Community forums and corroborated by multiple independent publications, are striking: one Galaxy S25 Ultra owner recorded a drop from 85% at midnight to just 5% by midday, with only two hours and nine minutes of active screen time logged in that window. The device lost somewhere between 5% and 7% of its charge every hour it sat idle on a flat surface — a rate that had never appeared before the July update. Another S25 Ultra user saw daily battery usage jump to 143% after the patch, up from roughly 80% before, while actually spending less time on the phone.

The drain is not the only problem. Devices are running noticeably hot even when idle, and at least one Galaxy S24 Ultra owner in Europe documented charging times tripling: a full charge that previously took around 70 minutes stretched to as long as three hours after the update was applied.

What the July 2026 Patch Was Supposed to Do

Samsung's July 2026 security update arrived as a standard monthly maintenance release for the One UI 8.5 firmware cycle. The patch addressed 57 documented security vulnerabilities in Galaxy phones and tablets — 41 sourced from Google's Android Security Bulletin and 16 Samsung-specific fixes — including five critical-severity flaws in components such as KnoxGuardManager and Samsung image codec libraries. Monthly security patches of this kind close real, exploitable vulnerabilities that could expose banking credentials, two-factor authentication codes, and private files. The patch was not optional in any meaningful sense.

What it was not supposed to do was disable reliable battery life on two of Samsung's most expensive smartphones.

Stuck CPU Loop: What Is Actually Happening Inside the Phone

The likely mechanism behind the drain is a stuck partial wakelock — a specific type of background process failure documented in Android's own developer guidelines.

Here is how it works in plain terms: Android normally puts the phone's processor into a very low power "sleep" state when the screen is off and no active tasks are running. This deep sleep is what allows a fully charged phone to sit in a pocket all day and still have most of its battery intact when you pick it up. An application or system service that needs to run a background job — syncing data, completing a cloud backup, reindexing content — temporarily "wakes" the CPU using a mechanism called a partial wakelock, does its work, and then releases the lock so the processor can sleep again.

When a wakelock gets stuck — either because the background job fails to complete cleanly, or because a firmware update disrupts the power management layer that normally releases them — the CPU stays awake indefinitely. It consumes power at a rate many times higher than deep sleep, generates heat, and never shows up accurately in the battery usage breakdown a user can see in Settings, because this type of consumption happens at the operating system level rather than inside any specific app. That is exactly what Samsung's own Device Care tool flagged on some affected S25 Ultra units: "Some apps or processes are overloading the system (CPU). Your device needs to restart," as reported in the Samsung Community forum.

Google's own Android Vitals framework considers wakelock usage "excessive" when it runs for more than two hours in a 24-hour period in more than 5% of user sessions. The 5–7% hourly drain documented on affected Galaxy Ultra units implies a wakelock that is near-continuous — far beyond what Google's threshold was designed to flag.

In at least one documented case, the stuck background job was a WhatsApp encrypted backup that failed to complete and became permanently looped. Canceling the stuck backup stopped the drain in that specific case. But the range of affected users is far too broad to be explained by WhatsApp backups alone.

One technical analysis of the regression noted that Samsung's Galaxy battery performance "leans heavily on aggressive One UI-side power management rather than raw hardware efficiency," which means a patch that disrupts that management layer can produce battery losses out of proportion to what a small firmware change might suggest. The firmware version linked to the issue on affected S25 Ultra models carries the build identifier CZG3.

The July 2026 patch also removed users' most powerful diagnostic workaround: Samsung quietly eliminated the full cache partition wipe option from the recovery menu in its February 2026 security patch, leaving the workarounds currently circulating on community forums — individual app cache clears, battery stats resets, safe mode isolation tests — as less targeted substitutes.

History Repeating on Galaxy Ultra Devices

This is not the first time a Samsung security patch has triggered this kind of regression. The pattern is now documented across at least five separate incidents in three years. Samsung's One UI 5.1 update introduced excessive battery drain traced to the Samsung Keyboard app, which Samsung acknowledged only after a support employee confirmed it in a community forum post — and fixed through a Galaxy Store update, not a full firmware patch. One UI 7 caused similar drain on Galaxy S24 and Galaxy Z Fold 5 devices in 2025; the issue resolved quietly with the June 2025 security patch. In October 2025, Samsung pulled One UI 8 entirely from the Galaxy S23 lineup when battery complaints reached a critical volume. The One UI 8.5 stable release then triggered fresh drain complaints on Galaxy Z Fold 7 devices in May and June 2026, addressed through maintenance patches and Galaxy Store updates.

Each cycle has followed the same script: users report, Samsung stays silent, a subsequent patch addresses the regression without a public acknowledgement that the prior update caused it.

A Samsung Community moderator — a Samsung employee — came closest to an acknowledgement in a response to one of the current forum threads: the behavior "may be related to a software optimisation issue introduced with the update rather than an individual device problem," the moderator wrote, asking users to submit diagnostic logs through the Samsung Members app. That is not a public statement and not an official press acknowledgement, but it is a meaningful departure from silence.

Samsung has not issued any public statement on the July 2026 regression.

What Galaxy Ultra Owners Can Try Right Now

No official fix exists as of this writing. A firmware maintenance update — possibly the August 2026 security patch — may address the regression, as has happened in past cycles. In the meantime, users on the community forums have documented several workarounds with varying success:

Check background activity. Navigate to Settings → Battery and Device Care → Battery → Battery Usage and look for any application showing unusually high background consumption. Force-stop and clear the cache for anything suspicious, starting with cloud backup clients including Google, Samsung Cloud, WhatsApp, and Dropbox.

Pause cloud backups. Disabling automatic backup scheduling — particularly WhatsApp's encrypted backup — eliminates one of the most commonly documented triggering conditions for the stuck wakelock.

Use deep sleep mode. Settings → Battery and Device Care → Battery → Background Usage Limits → Deep Sleeping Apps. Adding infrequently-used applications here prevents them from acquiring background wakelocks altogether.

Reset battery stats. Open the phone dialer and enter *#9900#, then select "Battery stats Reset." This clears the power management system's accumulated data and may help the OS reassess background process behavior.

Boot into safe mode. Holding the power button, then long-pressing "Power off" to enter safe mode, disables all third-party applications. If the drain stops in safe mode, the cause is a third-party app rather than a system-level firmware bug.

Disable RAM Plus and nearby device scanning. Multiple community members report marginal improvement from turning these off in developer options and connectivity settings, reducing background system activity.

None of these addresses the root cause, and none of them should be necessary on a device retailing at $1,299.99. They are stopgap measures.

Samsung's Silence Is the Problem's Second Act

The July 2026 regression reveals two distinct failures, not one. The first is a QA failure: a security patch passed testing and was shipped globally while carrying a power management defect severe enough to make a flagship phone unreliable as a daily device. The second is a communication failure: Samsung has no established mechanism for publicly acknowledging post-patch regressions, and its track record across five documented incidents suggests it does not intend to build one.

The dilemma this creates for affected users is real. The July patch closes five critical security vulnerabilities that genuinely matter — rolling back the update is not supported on consumer Galaxy devices and would reopen those vulnerabilities. The only path is forward: wait for a maintenance update that may or may not arrive before August, submit diagnostic logs through Samsung Members, and apply workarounds that may or may not help.

Galaxy S25 Ultra and S24 Ultra owners paid premium prices for devices Samsung markets as the company's most capable Android smartphones. Battery life, thermal behavior, and charging speed are not secondary features — they are the reason those devices command a four-figure price tag. A security patch that compromises all three simultaneously, deployed to a global fleet of millions of devices with no acknowledgement and no committed timeline for resolution, is not a minor inconvenience.

Frequently Asked Questions

Why is my Samsung Galaxy S25 Ultra battery draining so fast after the July update?

The most likely cause is a stuck partial wakelock introduced by the July 2026 One UI 8.5 security patch (build CZG3 on affected S25 Ultra units). A partial wakelock is a mechanism that keeps the phone's processor running even when the screen is off. When one gets stuck — due to a failed background job or a power management disruption in the firmware — the CPU stays active continuously, burning battery at several times the normal idle rate without appearing in the standard battery usage breakdown in Settings. Samsung's Device Care tool may display a warning reading "Some apps or processes are overloading the system (CPU). Your device needs to restart," which is the clearest indicator of this condition, as confirmed in the Samsung Community forum.

How do I fix the Galaxy Ultra battery drain after the July 2026 Samsung update?

No official fix exists yet. In the meantime, check Settings → Battery and Device Care → Battery Usage for any app with unusually high background activity, particularly backup clients like WhatsApp. Disabling automatic cloud backups has resolved the issue for some users. Entering safe mode (hold power, then long-press "Power off") can help determine whether a third-party app is the trigger. Resetting battery stats via the dialer code *#9900# → Battery stats Reset is another option community members have reported modest success with. If the drain is from a system-level firmware bug rather than an app, these steps may reduce but not eliminate it until Samsung ships a maintenance patch.

Has Samsung acknowledged or fixed the July 2026 battery drain issue?

Not officially. A Samsung Community moderator — a Samsung employee — wrote in a forum thread that the behavior "may be related to a software optimisation issue introduced with the update rather than an individual device problem" and asked users to submit diagnostic logs through the Samsung Members app. That is the extent of the public record as of July 29, 2026. Samsung has not issued a press statement, a help center article, or a committed repair timeline. The company's track record across five similar regression incidents since 2023 suggests the fix will arrive in a subsequent monthly security patch, most likely August 2026, without a public acknowledgement that the July patch caused the regression, as documented in the forum thread.

Should I install the Samsung July 2026 security patch if I have not already?

The July 2026 patch closes 57 documented security vulnerabilities, including five rated critical-severity in Samsung system components. Leaving those vulnerabilities unpatched is a genuine security risk, particularly for users who rely on their phone for banking, two-factor authentication, or work applications. The battery drain regression is disruptive, but it is a software problem that Samsung can fix in a future update; an unpatched security vulnerability is a persistent exposure that can be exploited by third parties. Most security practitioners would advise installing the patch and applying the available workarounds while waiting for a maintenance fix, as outlined in the patch analysis.