The Linux kernel’s 9p virtual file system had a logic flaw in its write routine where the inode size (i_size) and the server’s reported size (remote_i_size) were not updated after a partial write, such as when the server returned a reduced byte count due to ENOSPC. Because the size remained stale, subsequent file operations could be based on an incorrect file length, potentially leading to data loss or corruption. This weakness is associated with CWE-252.

All Linux kernel releases that implement the 9p protocol without the commit 88871ab548c1d7b11cde9b04063f3c1c6fbd7039 are affected. Systems running earlier kernel versions and mounting 9p filesystems are at risk.

The CVSS score is 5.5, indicating moderate severity. The EPSS score is below 1% and the vulnerability is not listed in CISA’s KEV catalog, implying a very low probability of exploitation. An attacker would need local write access to a 9p‑mounted path and must trigger a truncated write, for example by exhausting the remote server’s space. Such conditions are unlikely in most deployments, and no remote code execution or privilege escalation is possible.