CVE-2025-71070
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2026-01-13

Last updated on: 2026-01-14

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: ublk: clean up user copy references on ublk server exit If a ublk server process releases a ublk char device file, any requests dispatched to the ublk server but not yet completed will retain a ref value of UBLK_REFCOUNT_INIT. Before commit e63d2228ef83 ("ublk: simplify aborting ublk request"), __ublk_fail_req() would decrement the reference count before completing the failed request. However, that commit optimized __ublk_fail_req() to call __ublk_complete_rq() directly without decrementing the request reference count. The leaked reference count incorrectly allows user copy and zero copy operations on the completed ublk request. It also triggers the WARN_ON_ONCE(refcount_read(&io->ref)) warnings in ublk_queue_reinit() and ublk_deinit_queue(). Commit c5c5eb24ed61 ("ublk: avoid ublk_io_release() called after ublk char dev is closed") already fixed the issue for ublk devices using UBLK_F_SUPPORT_ZERO_COPY or UBLK_F_AUTO_BUF_REG. However, the reference count leak also affects UBLK_F_USER_COPY, the other reference-counted data copy mode. Fix the condition in ublk_check_and_reset_active_ref() to include all reference-counted data copy modes. This ensures that any ublk requests still owned by the ublk server when it exits have their reference counts reset to 0.
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Meta Information
Published
2026-01-13
Last Modified
2026-01-14
Generated
2026-05-06
AI Q&A
2026-01-14
EPSS Evaluated
2026-05-05
NVD
CVE-2025-71070
EUVD
EUVD-2026-2263
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel to c5c5eb24ed61 (inc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability in the Linux kernel's ublk subsystem involves a reference count leak when a ublk server process releases a ublk character device file. Specifically, requests dispatched to the ublk server but not yet completed retain an incorrect reference count (UBLK_REFCOUNT_INIT). Due to an optimization in the code, the reference count was not decremented properly, allowing user copy and zero copy operations on completed requests, which should not happen. This can cause warnings and improper handling of requests. The fix ensures that all reference-counted data copy modes have their reference counts reset to zero when the ublk server exits.


How can this vulnerability impact me? :

The impact of this vulnerability is that it allows user copy and zero copy operations on completed ublk requests due to leaked reference counts. This improper handling could lead to unexpected behavior or resource leaks in the kernel, potentially causing system instability or crashes. It also triggers kernel warnings, which may affect system reliability or debugging.


What immediate steps should I take to mitigate this vulnerability?

To mitigate this vulnerability, update the Linux kernel to a version that includes the fix for the ublk reference count leak. The fix ensures that all reference-counted data copy modes have their reference counts reset to 0 when the ublk server exits, preventing the leak and associated issues.


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