CVE-2026-97926
HighCVSS 7.0Summary
In the Linux kernel, the UFS filesystem copied the cylinder group index and rotor positions from disk without validation, then used them as indices during allocation and free. A crafted image could set arbitrary values, causing writes outside the s_csp allocation or bitmap scans far past the cylinder group buffers. The fix rejects cylinder groups with mismatched index or out-of-group rotors.
Risk Assessment
This can lead to kernel memory corruption, system crash, or potential privilege escalation. It requires mounting a crafted UFS image.
Recommendation
Update the Linux kernel to a version containing the fix. Avoid mounting untrusted UFS filesystem images.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: ufs: validate cylinder group metadata before caching it ufs_read_cylinder() copies the cylinder group index and the rotor positions straight from the on-disk group and caches them without any check: ucpi->c_cgx = fs32_to_cpu(sb, ucg->cg_cgx); ucpi->c_rotor = fs32_to_cpu(sb, ucg->cg_rotor); ucpi->c_frotor = fs32_to_cpu(sb, ucg->cg_frotor); ucpi->c_irotor = fs32_to_cpu(sb, ucg->cg_irotor); They are then used as indices during allocation and free: - c_cgx indexes the cylinder summary array as UFS_SB(sb)->fs_cs(ucpi->c_cgx), so a value past s_ncg writes a 32 bit count outside the s_csp allocation. - c_frotor becomes a bitmap scan start, start = c_frotor >> 3, and then length = ((s_fpg + 7) >> 3) - start. A start beyond the block bitmap wraps the unsigned length to a huge value, so ubh_scanc() walks far past the cylinder group buffers. c_irotor drives the inode bitmap the same way. A crafted image can set any of these freely, turning an ordinary allocation into an out of bounds access. Reject a cylinder group whose recorded index does not match the group being read, or whose rotors fall outside the group, before the metadata is cached. Valid filesystems keep cg_cgx equal to the group number and the rotors within the group, so only malformed images are rejected.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS