An integer underflow in the Linux kernel's jbd2 journaling subsystem allows the function that sets up fast commit to corrupt internal journal metadata. The subtraction that checks journal capacity wraps when the number of fast‑commit blocks exceeds the last block, bypassing the bounds check. This overwrites pointers that track journal usage, leading to a journal abort and potentially causing data loss on the affected file system. The weakness is an integer underflow.

All Linux kernels that include the jbd2 journaling module and have not yet applied the guard commit are affected. Any system running the vulnerable code, regardless of distribution, is impacted.

The CVSS score of 7.8 indicates a high‑severity flaw. The EPSS score of < 1 % suggests a low exploitation probability, and the vulnerability is not listed in CISA’s KEV catalog. Based on the description, it is inferred that the attack vector is local; an attacker with the ability to affect journaling activity—such as a privileged process or a compromised user with write access to the journaling file system—could trigger the fault. No remote exploitation path is documented, and the impact on confidentiality is low, but integrity and availability are threatened.