Linux: Use After Free
CVE-2025-21739 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 0a6895c03b1f439236e2d22b1a69ebfc1eb9d5ea, d06eb2620d3bf16056b8b7ea3744dbb5e30512f4, 0dc539b888fb5f56b6eeddd95433eab557d4b0c1 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.22% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 0a6895c03b1f439236e2d22b1a69ebfc1eb9d5ea or d06eb2620d3bf16056b8b7ea3744dbb5e30512f4 or 0dc539b888fb5f56b6eeddd95433eab557d4b0c1 or 0c77c0d754fe83cb154715fcfec6c3faef94f207, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.14 or 6.13.3, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | d76d9d7d1009968dd3a0fc30e5f5ee9fbffc1350 up to, but not including, 0a6895c03b1f439236e2d22b1a69ebfc1eb9d5ea; d76d9d7d1009968dd3a0fc30e5f5ee9fbffc1350 up to, but not including, d06eb2620d3bf16056b8b7ea3744dbb5e30512f4; d76d9d7d1009968dd3a0fc30e5f5ee9fbffc1350 up to, but not including, 0dc539b888fb5f56b6eeddd95433eab557d4b0c1; d76d9d7d1009968dd3a0fc30e5f5ee9fbffc1350 up to, but not including, 0c77c0d754fe83cb154715fcfec6c3faef94f207; d76d9d7d1009968dd3a0fc30e5f5ee9fbffc1350 up to, but not including, 9c185beae09a3eb85f54777edafa227f7e03075d; d76d9d7d1009968dd3a0fc30e5f5ee9fbffc1350 up to, but not including, f8fb2403ddebb5eea0033d90d9daae4c88749ada; 5.12 | 0a6895c03b1f439236e2d22b1a69ebfc1eb9d5ea, d06eb2620d3bf16056b8b7ea3744dbb5e30512f4, 0dc539b888fb5f56b6eeddd95433eab557d4b0c1, 0c77c0d754fe83cb154715fcfec6c3faef94f207, 9c185beae09a3eb85f54777edafa227f7e03075d, f8fb2403ddebb5eea0033d90d9daae4c88749ada |
| Linux | Linux Kernel | 5.12 up to, but not including, 6.12.14; 6.13 up to, but not including, 6.13.3; 6.14 | 6.12.14, 6.13.3 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CISA (ADP).
Official 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
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The 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.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
Recent Use After Free vulnerabilities
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