CVE-2026-53130: fs/omfs: reject s_sys_blocksize smaller than OMFS_DIR_START
In the Linux kernel, the following vulnerability has been resolved:
fs/omfs: reject ssysblocksize smaller than OMFSDIRSTART
omfsfillsuper() rejects oversized ssysblocksize values (> PAGESIZE), but it does not reject values smaller than OMFSDIRSTART (0x1b8 = 440).
Later, omfsmakeempty() uses
sbi->ssysblocksize - OMFSDIRSTART
as the length argument to memset(). Since ssysblocksize is u32, a crafted filesystem image with ssysblocksize < OMFSDIRSTART causes an unsigned underflow there, wrapping to a value near 2^32. That drives a ~4 GiB memset() from bh->bdata + OMFSDIRSTART and overwrites kernel memory far beyond the backing block buffer.
Add the corresponding lower-bound check alongside the existing upper-bound check in omfsfillsuper(), so that malformed images are rejected during superblock validation before any filesystem data is processed.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
In omfs_fill_super(), add/ensure a lower-bound check to reject malformed filesystem images where s_sys_blocksize is smaller than OMFS_DIR_START (0x1b8 = 440), in addition to the existing upper-bound check (> PAGE_SIZE), so memset() cannot be driven by an unsigned underflow.
Linux kernel omfs filesystem (fs/omfs) s_sys_blocksize lower-bound validation in omfs_fill_super() = Reject if s_sys_blocksize < OMFS_DIR_START (0x1b8 = 440)
Event History
Frequently Asked Questions
What is the severity of CVE-2026-53130?
CVE-2026-53130 has a risk rating of 80, indicating a high severity level.
How do I fix CVE-2026-53130?
To fix CVE-2026-53130, you should apply the latest Linux kernel updates that address the vulnerability.
What systems are affected by CVE-2026-53130?
CVE-2026-53130 affects the Linux kernel, specifically instances using the OMFS filesystem.
What issue does CVE-2026-53130 address?
CVE-2026-53130 addresses the improper rejection of s_sys_blocksize values smaller than OMFS_DIR_START.
When was CVE-2026-53130 published?
CVE-2026-53130 was published on June 24, 2026.