CVE-2026-64421 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
media: nxp: imx8-isi: Fix use-after-free on remove
KASAN reports a slab-use-after-free in __media_entity_remove_link() during rmmod of imx8_isi:
BUG: KASAN: slab-use-after-free in __media_entity_remove_link+0x608/0x650 Read of size 2 at addr ffff0000d47cb02a by task rmmod/724
Call trace: __media_entity_remove_link+0x608/0x650 __media_entity_remove_links+0x78/0x144 __media_device_unregister_entity+0x150/0x280 media_device_unregister_entity+0x48/0x68 v4l2_device_unregister_subdev+0x158/0x300 v4l2_async_unbind_subdev_one+0x22c/0x358 v4l2_async_nf_unbind_all_subdevs+0xfc/0x1c0 v4l2_async_nf_unregister+0x5c/0x14c mxc_isi_remove+0x124/0x2a0 [imx8_isi]
Allocated by task 249: __kmalloc_noprof+0x27c/0x690 mxc_isi_crossbar_init+0x22c/0x560 [imx8_isi]
Freed by task 724: kfree+0x1e4/0x5b0 mxc_isi_crossbar_cleanup+0x34/0x80 [imx8_isi]
mxc_isi_remove+0x11c/0x2a0 [imx8_isi]
The problem is that mxc_isi_remove() calls mxc_isi_crossbar_cleanup() before mxc_isi_v4l2_cleanup(). The crossbar cleanup frees the media entity pads, but the subsequent v4l2 cleanup still tries to remove media links that reference those pads.
Fix this by calling mxc_isi_v4l2_cleanup() before mxc_isi_crossbar_cleanup() to ensure all media entities are properly unregistered while the pads are still valid.
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Analysis
by VulDB Data Team • 07/25/2026
The vulnerability in question involves a use-after-free condition within the Linux kernel's media subsystem, specifically affecting the nxp imx8-isi driver. This issue manifests during module removal operations when the rmmod command attempts to unload the imx8_isi kernel module. The kernel's KASAN (Kernel Address Sanitizer) detection system identifies a slab-use-after-free error occurring in the __media_entity_remove_link() function, indicating that memory previously freed is being accessed. The problematic memory address ffff0000d47cb02a shows a read operation of size 2, suggesting an attempt to access data within a freed memory slab that should no longer be valid.
The call trace reveals the sequence of function calls leading to this vulnerability, beginning with mxc_isi_remove() which orchestrates the cleanup process. The execution path flows through __media_entity_remove_links(), __media_device_unregister_entity(), and v4l2_device_unregister_subdev() before reaching the critical __media_entity_remove_link() function. This progression demonstrates how the driver's cleanup mechanism fails to maintain proper ordering of resource deallocation, creating a temporal window where media entities remain registered while their underlying memory structures have been freed.
The root cause stems from improper cleanup sequence within the mxc_isi_remove() function, where mxc_isi_crossbar_cleanup() is invoked before mxc_isi_v4l2_cleanup(). This ordering flaw creates a scenario where crossbar cleanup operations release media entity pads and associated resources, while v4l2 cleanup attempts to reference these same memory structures during link removal operations. The allocation history shows that the problematic memory was originally allocated through __kmalloc_noprof() within mxc_isi_crossbar_init(), establishing the memory pool that gets prematurely freed. The freeing operation occurs via kfree() in mxc_isi_crossbar_cleanup(), which directly precedes the v4l2 cleanup phase where the use-after-free condition manifests.
This vulnerability aligns with CWE-416, representing a classic use-after-free scenario where memory is accessed after it has been freed, and can be categorized under ATT&CK technique T1059.006 for kernel-level code execution vulnerabilities. The impact extends beyond simple memory corruption to potentially enable privilege escalation or system instability during normal module removal operations. The fix implemented involves reordering the cleanup functions to ensure mxc_isi_v4l2_cleanup() executes before mxc_isi_crossbar_cleanup(), thereby guaranteeing that all media entities are properly unregistered and their associated links removed while the pad structures remain valid in memory.
The remediation addresses a fundamental synchronization issue in kernel module lifecycle management, where proper resource ordering is critical for preventing temporal inconsistencies. This fix ensures that during module removal, all references to media entities are resolved and cleaned up before the underlying memory structures that support those entities are freed. The solution maintains the integrity of the media framework's entity management system while preserving the functional requirements of both crossbar and v4l2 cleanup operations. This vulnerability represents a common class of kernel-level memory safety issues that can be particularly dangerous in embedded systems where module loading/unloading cycles occur frequently, as demonstrated by the imx8-isi driver's role in multimedia processing for NXP i.MX 8 SoC platforms.