CVE-2025-21739: linux Use After Free

Vulnerability summary

CVE-2025-21739 is a high (CVSS 7.8) Use After Free vulnerability in linux. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 12% of scored vulnerabilities.

Timeline

1. 27-02-2025
   PublishedVulnerability first disclosed.
2. 01-06-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: scsi: ufs: core: Fix use-after free in init error and remove paths devm_blk_crypto_profile_init() registers a cleanup handler to run when the associated (platform-) device is being released. For UFS, the crypto private data and pointers are stored as part of the ufs_hba's data structure 'struct ufs_hba::crypto_profile'. This structure is allocated as part of the underlying ufshcd and therefore Scsi_host allocation. During driver release or during error handling in ufshcd_pltfrm_init(), this structure is released as part of ufshcd_dealloc_host() before the (platform-) device associated with the crypto call above is released. Once this device is released, the crypto cleanup code will run, using the just-released 'struct ufs_hba::crypto_profile'. This causes a use-after-free situation: Call trace: kfree+0x60/0x2d8 (P) kvfree+0x44/0x60 blk_crypto_profile_destroy_callback+0x28/0x70 devm_action_release+0x1c/0x30 release_nodes+0x6c/0x108 devres_release_all+0x98/0x100 device_unbind_cleanup+0x20/0x70 really_probe+0x218/0x2d0 In other words, the initialisation code flow is: platform-device probe ufshcd_pltfrm_init() ufshcd_alloc_host() scsi_host_alloc() allocation of struct ufs_hba creation of scsi-host devices devm_blk_crypto_profile_init() devm registration of cleanup handler using platform-device and during error handling of ufshcd_pltfrm_init() or during driver removal: ufshcd_dealloc_host() scsi_host_put() put_device(scsi-host) release of struct ufs_hba put_device(platform-device) crypto cleanup handler To fix this use-after free, change ufshcd_alloc_host() to register a devres action to automatically cleanup the underlying SCSI device on ufshcd destruction, without requiring explicit calls to ufshcd_dealloc_host(). This way: * the crypto profile and all other ufs_hba-owned resources are destroyed before SCSI (as they've been registered after) * a memleak is plugged in tc-dwc-g210-pci.c remove() as a side-effect * EXPORT_SYMBOL_GPL(ufshcd_dealloc_host) can be removed fully as it's not needed anymore * no future drivers using ufshcd_alloc_host() could ever forget adding the cleanup

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.