CVE-2025-39901
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-01

Last updated on: 2025-12-12

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: i40e: remove read access to debugfs files The 'command' and 'netdev_ops' debugfs files are a legacy debugging interface supported by the i40e driver since its early days by commit 02e9c290814c ("i40e: debugfs interface"). Both of these debugfs files provide a read handler which is mostly useless, and which is implemented with questionable logic. They both use a static 256 byte buffer which is initialized to the empty string. In the case of the 'command' file this buffer is literally never used and simply wastes space. In the case of the 'netdev_ops' file, the last command written is saved here. On read, the files contents are presented as the name of the device followed by a colon and then the contents of their respective static buffer. For 'command' this will always be "<device>: ". For 'netdev_ops', this will be "<device>: <last command written>". But note the buffer is shared between all devices operated by this module. At best, it is mostly meaningless information, and at worse it could be accessed simultaneously as there doesn't appear to be any locking mechanism. We have also recently received multiple reports for both read functions about their use of snprintf and potential overflow that could result in reading arbitrary kernel memory. For the 'command' file, this is definitely impossible, since the static buffer is always zero and never written to. For the 'netdev_ops' file, it does appear to be possible, if the user carefully crafts the command input, it will be copied into the buffer, which could be large enough to cause snprintf to truncate, which then causes the copy_to_user to read beyond the length of the buffer allocated by kzalloc. A minimal fix would be to replace snprintf() with scnprintf() which would cap the return to the number of bytes written, preventing an overflow. A more involved fix would be to drop the mostly useless static buffers, saving 512 bytes and modifying the read functions to stop needing those as input. Instead, lets just completely drop the read access to these files. These are debug interfaces exposed as part of debugfs, and I don't believe that dropping read access will break any script, as the provided output is pretty useless. You can find the netdev name through other more standard interfaces, and the 'netdev_ops' interface can easily result in garbage if you issue simultaneous writes to multiple devices at once. In order to properly remove the i40e_dbg_netdev_ops_buf, we need to refactor its write function to avoid using the static buffer. Instead, use the same logic as the i40e_dbg_command_write, with an allocated buffer. Update the code to use this instead of the static buffer, and ensure we free the buffer on exit. This fixes simultaneous writes to 'netdev_ops' on multiple devices, and allows us to remove the now unused static buffer along with removing the read access.
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Meta Information
Published
2025-10-01
Last Modified
2025-12-12
Generated
2026-05-07
AI Q&A
2025-10-01
EPSS Evaluated
2026-05-05
NVD
CVE-2025-39901
Affected Vendors & Products
Showing 6 associated CPEs
Vendor Product Version / Range
linux linux_kernel From 3.12 (inc) to 6.12.46 (exc)
linux linux_kernel From 6.13 (inc) to 6.16.6 (exc)
linux linux_kernel 6.17
linux linux_kernel 6.17
linux linux_kernel 6.17
linux linux_kernel 6.17
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-125 The product reads data past the end, or before the beginning, of the intended buffer.
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability involves the i40e driver in the Linux kernel, specifically its debugfs files 'command' and 'netdev_ops'. These files use a static 256-byte buffer that is shared across devices and implemented with questionable logic. The 'netdev_ops' file can be exploited by carefully crafted input to cause an overflow in snprintf, potentially allowing reading of arbitrary kernel memory. The vulnerability arises because the read functions use this static buffer without proper locking, and the buffer can be accessed simultaneously, leading to possible memory exposure. The fix was to remove read access to these debugfs files and refactor the write function to avoid using the static buffer, preventing overflow and simultaneous write issues.


How can this vulnerability impact me? :

This vulnerability can impact you by potentially allowing an attacker to read arbitrary kernel memory through the 'netdev_ops' debugfs file if they craft specific input. This could lead to exposure of sensitive kernel data or system information. However, the 'command' file is not exploitable in this way. The overall impact is limited to information disclosure via a legacy debug interface, which has been mitigated by removing read access to these files.


What immediate steps should I take to mitigate this vulnerability?

The vulnerability is mitigated by removing read access to the 'command' and 'netdev_ops' debugfs files in the i40e driver. Immediate steps include updating the Linux kernel to a version where this fix is applied, which disables read access to these debugfs files, preventing potential arbitrary kernel memory reads. Additionally, avoid using these debugfs interfaces as they are legacy and mostly useless, and rely on more standard interfaces to obtain netdev information.


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