Linux Kernel up to 6.18.13/6.19.3 fbnic fbnic_fw_log_write null pointer dereference

Summaryinfo

A vulnerability identified as critical has been detected in Linux Kernel up to 6.18.13/6.19.3. Affected by this issue is the function fbnic_fw_log_write of the component fbnic. This manipulation causes null pointer dereference. This vulnerability is registered as CVE-2026-45977. No exploit is available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.13/6.19.3. It has been declared as critical. Affected by this vulnerability is the function fbnic_fw_log_write of the component fbnic. The manipulation with an unknown input leads to a null pointer dereference vulnerability. The CWE definition for the vulnerability is CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. As an impact it is known to affect availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: fbnic: close fw_log race between users and teardown Fixes a theoretical race on fw_log between the teardown path and fw_log write functions. fw_log is written inside fbnic_fw_log_write() and can be reached from the mailbox handler fbnic_fw_msix_intr(), but fw_log is freed before IRQ/MBX teardown during cleanup, resulting in a potential data race of dereferencing a freed/null variable. Possible Interleaving Scenario: CPU0: fbnic_fw_msix_intr() // Entry fbnic_fw_log_write() if (fbnic_fw_log_ready()) // true ... preempt ... CPU1: fbnic_remove() // Entry fbnic_fw_log_free() vfree(log->data_start); log->data_start = NULL; CPU0: continues, walks log->entries or writes to log->data_start The initialization also has an incorrect order problem, as the fw_log is currently allocated after MBX setup during initialization. Fix the problems by adjusting the synchronization order to put initialization in place before the mailbox is enabled, and not cleared until after the mailbox has been disabled.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2026-45977 since 05/13/2026. The exploitation appears to be difficult. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 6.18.14 or 6.19.4 eliminates this vulnerability. Applying the patch 223cfef4812bdfa5ac5c1aa761cdba03cfe2c9cd/5f10ab3643c58a22fbaee92c4701b00fcb4a465d/ee5492fd88cfc079c19fbeac78e9e53b7f6c04f3 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.19.0
• 6.19.1
• 6.19.2
• 6.19.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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