UBUNTU-CVE-2026-89891: Use After Free
In the Linux kernel, the following vulnerability has been resolved: media: em28xx: fix use-after-free of devnext->devlist on disconnect When a device with hasdualts=1 is probed and the isaudioonly path is taken, both dev and dev->devnext are added to the global em28xxdevlist via em28xxinitextension(). However, during disconnect, em28xxcloseextension(dev) only calls listdel(&dev->devlist), leaving dev->devnext->devlist still linked in the global list. When devnext is subsequently freed via krefput(), its devlist entry becomes a dangling pointer in em28xxdevlist. The next device probe that calls em28xxinitextension() triggers a list corruption BUG when listaddtail detects the freed node. This bug was exposed by commit a368ecde8a50 ("USB: core: Fix duplicate endpoint bug by clearing reserved bits in the descriptor") which clears reserved bits in bEndpointAddress during endpoint parsing. This causes fuzzed endpoint addresses like 0xf3 to be normalized to 0x83, which em28xx interprets as a vendor audio endpoint, enabling the isaudioonly + hasdualts code path that was previously unreachable with such descriptors. Fix this by removing dev->devnext->devlist from the global list in em28xxcloseextension() before the device is freed.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1 - Compensating control
In em28xx_close_extension(), remove dev->dev_next->devlist from the global em28xx_devlist before dev_next is freed.
Event History
Frequently Asked Questions
Which systems are exposed to this issue?
Systems running one of the listed Ubuntu kernel packages are exposed when they use an em28xx device that has dual transport-stream support and enters the audio-only probe path. The failure occurs during device disconnect and can be triggered by a later device probe.
What conditions are needed to trigger the bug?
A device must be probed with has_dual_ts=1 while the is_audio_only path is taken. Fuzzed endpoint addresses that are normalized to a vendor audio endpoint can make this path reachable; after the device disconnects, probing another device can trigger list-corruption detection.
How can I tell whether the issue has already occurred?
The described symptom is a list-corruption BUG during em28xx initialization when a subsequent device is probed after the affected device was disconnected. The underlying condition is a freed dev_next list entry remaining in the global em28xx device list.