CVE-2026-53130
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
In the Linux kernel's OMFS filesystem, a missing lower-bound check for s_sys_blocksize allows a crafted image with a value smaller than OMFS_DIR_START (440) to cause an unsigned integer underflow in omfs_make_empty(). This triggers a memset() with a length near 4 GiB, overwriting kernel memory beyond the block buffer.
Risk Assessment
The organization faces local privilege escalation or system crash (kernel panic) by mounting a malicious OMFS image. An attacker with filesystem mount access could potentially gain kernel-level control.
Recommendation
Immediately apply the Linux kernel patch that adds a lower-bound check for s_sys_blocksize in omfs_fill_super(). Update the kernel to a patched version or backport the fix.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: fs/omfs: reject s_sys_blocksize smaller than OMFS_DIR_START omfs_fill_super() rejects oversized s_sys_blocksize values (> PAGE_SIZE), but it does not reject values smaller than OMFS_DIR_START (0x1b8 = 440). Later, omfs_make_empty() uses sbi->s_sys_blocksize - OMFS_DIR_START as the length argument to memset(). Since s_sys_blocksize is u32, a crafted filesystem image with s_sys_blocksize < OMFS_DIR_START causes an unsigned underflow there, wrapping to a value near 2^32. That drives a ~4 GiB memset() from bh->b_data + OMFS_DIR_START and overwrites kernel memory far beyond the backing block buffer. Add the corresponding lower-bound check alongside the existing upper-bound check in omfs_fill_super(), so that malformed images are rejected during superblock validation before any filesystem data is processed.