Apple's C1 Modem Gets First Security Update in iOS 18.5

The iOS 18.5 update that Apple released today includes a security fix for the iPhone 16e's C1 modem, which is the first Apple-designed modem.

Apple iPhone 16e C1 Feature
According to Apple's security support document for iOS 18.5, there's a fix for a vulnerability with the C1 modem. Apple says that it addressed a baseband security flaw that could allow an attacker "in a privileged network position" to intercept network traffic. Basically, a hacker that had access to cellular network infrastructure could potentially exploit the vulnerability for surveillance or to employ a man-in-the-middle attack.

The C1's baseband is used for signal processing, so it encodes and decodes data for communication between devices and networks, and processes calls, texts, and data connections. Apple addressed the vulnerability with improved state management, which could mean new validation checks to prevent attackers from exploiting weaknesses between operational states.

Apple released the ‌iPhone 16e‌ earlier this year, and today's security update is notable because it marks the first security flaw discovered and addressed in the C1 modem.

iOS 18.5 also includes several other security fixes for vulnerabilities with image processing, call history, Bluetooth, file parsing, FaceTime, Notes, ProRes, WebKit, and more. None of the vulnerabilities fixed today were known to have been actively exploited, but it's still a good idea to update right away.

Related Roundup: iPhone 16e
Buyer's Guide: iPhone 16e (Buy Now)
Related Forum: iPhone

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Top Rated Comments

mk313 Avatar
16 weeks ago
I'm a little surprised at how well the Apple Designed modems appear to be working. When Apple moved to the Intel Modems, there was a lot of pushback on the performance relative to the Qualcomm ones. It seems like people are satisfied with the Apple designed ones (for the most part) which is hopefully good news for the future.
Score: 6 Votes (Like | Disagree)
TechTexan Avatar
16 weeks ago

I'm a little surprised at how well the Apple Designed modems appear to be working. When Apple moved to the Intel Modems, there was a lot of pushback on the performance relative to the Qualcomm ones. It seems like people are satisfied with the Apple designed ones (for the most part) which is hopefully good news for the future.
I haven’t had any issues with mine, works the same if not better then my last phone.
Score: 5 Votes (Like | Disagree)
Unregistered 4U Avatar
16 weeks ago

Yes, I am also surprised how well the first iteration went. But I also remember the naysayers when the first M1 came out and it was beating Intel and AMD chips, people were skeptical and blamed flawed testing.
The countdown is on for when the EU will say that Apple using their own modems is anticompetitive and it doesn’t allow competition in the Apple cellular modem market. :)
Score: 4 Votes (Like | Disagree)
Hurda Avatar
16 weeks ago

but older versions are usually patched as well.
But not necessarily all known bugs are patched in these versions.

https://support.apple.com/guide/deployment/about-software-updates-depc4c80847a/web#dep25a4a6565
Note: Because of dependency on architecture and system changes to any current version of Apple operating systems (for example, macOS 15, iOS 18, and so on), not all known security issues are addressed in previous versions (for example, macOS 14, iOS 17, and so on).
Score: 2 Votes (Like | Disagree)
I7guy Avatar
16 weeks ago

MacRumors content image ('https://www.macrumors.com/2025/05/12/apple-ios-18-5-c1-security-fix/')

[…]

iOS 18.5 also includes several other security fixes for vulnerabilities with image processing, call history, Bluetooth, file parsing, FaceTime, Notes, ProRes, WebKit, and more. None of the vulnerabilities fixed today were known to have been actively exploited, but it's still a good idea to update right away.

Article Link: Apple's C1 Modem Gets First Security Update in iOS 18.5 ('https://www.macrumors.com/2025/05/12/apple-ios-18-5-c1-security-fix/')
The above is useful information for the main news article.
Score: 2 Votes (Like | Disagree)
iBluetooth Avatar
16 weeks ago

I'm a little surprised at how well the Apple Designed modems appear to be working. When Apple moved to the Intel Modems, there was a lot of pushback on the performance relative to the Qualcomm ones. It seems like people are satisfied with the Apple designed ones (for the most part) which is hopefully good news for the future.
Yes, I am also surprised how well the first iteration went. But I also remember the naysayers when the first M1 came out and it was beating Intel and AMD chips, people were skeptical and blamed flawed testing.
Score: 2 Votes (Like | Disagree)