iOS 26 Crash: _xzm_xzone_malloc_freelist_outlined in com.apple.network.connections

Hello Apple Support Team,

We are seeing a production crash on iOS 26 devices that appears to originate from Apple system frameworks rather than application code.

Crash Summary

• Crash signature: _xzm_xzone_malloc_freelist_outlined
• Crashed thread: com.apple.network.connections
• Frameworks involved: CFNetwork, Security, libdispatch, libsystem_malloc
• Affected OS: iOS 26.x
• App built with: Xcode 16
• Devices: Multiple models (not device-specific)
• Reproducibility: Intermittent, higher frequency during app launch / background networking

Observed Stack Trace (top frames)

• _xzm_xzone_malloc_freelist_outlined
• dispatch_data_create_alloc
• xpc_data_deserialize
• SecTrustEvaluateIfNecessary
• CFNetwork HTTPProtocol / HTTP3Connection
• com.apple.network.connections

App Context

• The app uses URLSession for networking.
• Multiple third-party SDKs are integrated (Firebase Analytics, Dynatrace, Appsflyer, and similar analytics/monitoring SDKs).
• These SDKs perform concurrent background network requests, especially during app launch and foreground transitions.
• No unsafe memory operations (manual malloc/free, unsafe pointers, or custom networking stacks) are used in the app code.

Key Observations

• The crash is predominantly observed on iOS 26 and not on earlier iOS versions.
• Stack traces do not include application symbols.
• Disabling or delaying analytics SDK initialization significantly reduces the crash rate.
• Reducing concurrent network requests and limiting HTTP/3 usage also mitigates the issue.
• This suggests a potential regression in CFNetwork / Network.framework / HTTP/3 handling combined with the new memory allocator (xzone) on iOS 26.

Impact

• Random app termination during background networking.
• Occurs without a clear deterministic repro path, making it difficult to fully mitigate at the app level.

Request Could you please help investigate whether this is a known iOS 26 issue related to:

• HTTP/3 / QUIC networking
• XPC deserialization
• Memory allocation in the new xzone allocator
• High-concurrency network requests

We would appreciate guidance on:

• Recommended mitigations
• Whether this issue is already tracked internally
• Any best practices for apps integrating multiple analytics SDKs on iOS 26

Crash logs and additional diagnostics can be provided if needed.

Thank you for your support.

Best regards, Dhananjay