UBUNTU-CVE-2026-68363: Use After Free
In the Linux kernel, the following vulnerability has been resolved: wifi: ath9k: hifusb: don't dereference hifdev after re-arming firmware request ath9khifrequestfirmware() re-arms an asynchronous firmware load via requestfirmwarenowait(), passing hifdev as the completion context, and then still dereferences hifdev: devinfo(&hifdev->udev->dev, "ath9khtc: Firmware %s requested\n", hifdev->fwname); The re-armed callback ath9khifusbfirmwarecb() runs on the "events" workqueue and, when the firmware is missing, walks the retry chain into ath9khifusbfirmwarefail() -> completeall(&hifdev->fwdone). That releases the waitforcompletion(&hifdev->fwdone) in a concurrent ath9khifusbdisconnect(), which then kfree()s hifdev. The trailing devinfo() in the frame that re-armed the request can therefore read freed memory (hifdev->udev, the first field of struct hifdeviceusb): BUG: KASAN: slab-use-after-free in ath9khifrequestfirmware Read of size 8 ... by task kworker/... ath9khifrequestfirmware ath9khifusbfirmwarecb drivers/net/wireless/ath/ath9k/hifusb.c:1247 requestfirmwareworkfunc Allocated by ...: ath9khifusbprobe drivers/net/wireless/ath/ath9k/hifusb.c Freed by ...: ath9khifusbdisconnect -> kfree drivers/net/wireless/ath/ath9k/hifusb.c The fwdone barrier only makes disconnect wait for the firmware chain to terminate; it does not protect the outer ath9khifrequestfirmware() frame that re-armed the request and keeps touching hifdev afterwards. Drop the post-request devinfo(): it is the only use of hifdev after the async request is armed, and it is purely informational (the deverr() on the failure path runs only when requestfirmwarenowait() did not arm a callback, so hifdev is still alive there). This was first reported by syzbot as a single, non-reproduced crash that was later auto-obsoleted, and was independently rediscovered by the reFuzz fuzzer, which produced a C reproducer (USB-gadget connect/disconnect of an ath9khtc device whose firmware download fails). The vulnerable code is unchanged and still present in v7.1-rc6, where the slab-use-after-free reproduces under KASAN once the (sub-microsecond) race window is widened.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-aws-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1117.124~20.04.1 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-147.147+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-38.38 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1016.16 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Compensating control
In ath9k_hif_request_firmware(), remove the post-request dev_info() that dereferences hif_dev after request_firmware_nowait() re-arms the asynchronous firmware request.
Event History
Frequently Asked Questions
Which systems are exposed to this issue?
Systems using the ath9k HTC USB Wi-Fi driver are relevant. The affected Ubuntu kernel package families listed are linux, linux-fips, linux-aws, linux-azure, linux-gcp, linux-aws-fips, linux-azure-fips, and linux-gcp-fips.
What conditions are required to trigger the use-after-free?
The driver must re-arm an asynchronous firmware request, the firmware request must fail because firmware is missing, and a concurrent USB-device disconnect must release and free the driver state while the original request path still accesses it.
What observable failure might indicate exposure?
A kernel memory-safety report may identify a KASAN slab-use-after-free in ath9k_hif_request_firmware, with ath9k_hif_usb_firmware_cb and request_firmware_work_func in the call chain. The affected access occurs after a firmware request is re-armed and the device is disconnected.