The issue is a race condition in the Firewire character device driver of the Linux kernel. The iso_resource_auto structure controls the state of a client resource; normally it advances through the sequence ISO_RES_AUTO_ALLOC → ISO_RES_AUTO_REALLOC → ISO_RES_AUTO_DEALLOC. Concurrent access from a work item and the file descriptor release function can trigger an unintended reversal from ISO_RES_AUTO_DEALLOC back to ISO_RES_AUTO_REALLOC, leaving the driver with an inconsistent resource state. This flaw is an instance of a concurrency error and also involves a potential deadlock scenario (CWE-366).

Affected systems are Linux kernel versions that include the Firewire subsystem and that have not yet integrated the commit that removes the back‑transition bug. The commit identifiers c6b51091cafff9ce6c03c1416aa13864d17ab97c and ee1df60a0d0e8ab4b00137135733bdadd6d33dab embed the fix; any kernel package lacking these commits remains vulnerable.

The CVSS score of 4.7 indicates moderate impact; the EPSS score of <1% indicates very low exploitation probability, and there is no KEV listing. The likely attack vector is a local attacker who can trigger the race by consecutively opening and closing a Firewire device while the kernel handles work-item routines. Based on the description, it is inferred that such concurrent operations would provoke the back‑transition state change.