iPhone update to 15.8.7 fails due to corrupt firmware file

Question

iPhone update to 15.8.7 fails due to corrupt firmware file

Every time I try to update my iPhone to 15.8.7, I get the error: The iPhone "Test's iPhone" could not be updated because the firmware file was corrupt. Disconnect and reconnect, then try again."

I follow the steps:

Connect my iPhone to Mac mini.
Open Finder, select my iPhone. Then I click Update. The downloading starts. After about 30 minutes, entire package of 5.27Gb is downloaded and I get the error.

What should I do?

Posted on Apr 7, 2026 1:04 AM

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Answer 1

Apr 8, 2026 12:50 AM in response to Valery Kuznetsov

Update via OTA

Settings, General, Software update.

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Answer 2

Apr 8, 2026 1:43 AM in response to Valery Kuznetsov

I was able to install iOS 15.8.7 using a MacBook Pro.

The difference is that on the Mac mini, I selected Download and Update from Finder, and on the MPB, I selected Download and only then Update.

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Answer 3

SravanKrA

Level 10

436,056 points

Apr 7, 2026 11:40 PM in response to Valery Kuznetsov

Do not download the firmware and update the iOS:

There are only 2 ways to update an iOS/iPadOS. Know how to...

Update Over-the-Air (OTA) —> Update your iPhone or iPad - Apple Support (IN)
Update using iTunes/Finder —> Update your iPhone, iPad, or iPod touch - Apple Support (IN)

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Answer 4

Apr 8, 2026 12:17 AM in response to SravanKrA

Thanks for the quick response.

I'm not downloading firmware. I use Finder to update my iPhone. I've successfully updated all previous versions of iOS. Finder gives the error a few seconds after the download is complete.

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