CVE-2026-45977 fbnic: close fw_log race between users and teardown
A race condition in the fbnic driver allows a use-after-free or null dereference during teardown, potentially causing a kernel crash.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-45977?
CVE-2026-45977 is a medium-severity vulnerability in Linux kernel, published on 27 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-45977?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-45977?
Apply the vendor's patch.
Is CVE-2026-45977 being exploited?
There is no known exploitation of CVE-2026-45977 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-45977, DEBIAN-CVE-2026-45977, GHSA-fgxx-jh4j-vgpg, UBUNTU-CVE-2026-45977.