CVE-2025-40190: Linux

High severity, CVSS 7.8. EPSS: 0.2% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: ext4: guard against EA inode refcount underflow in xattr update syzkaller found a path where ext4_xattr_inode_update_ref() reads an EA inode refcount that is already <= 0 and then applies ref_change (often -1). That lets the refcount underflow and we proceed with a bogus value, triggering errors like: EXT4-fs error: EA inode <n> ref underflow: ref_count=-1 ref_change=-1 EXT4-fs warning: ea_inode dec ref err=-117 Make the invariant explicit: if the current refcount is non-positive, treat this as on-disk corruption, emit ext4_error_inode(), and fail the operation with -EFSCORRUPTED instead of updating the refcount. Delete the WARN_ONCE() as negative refcounts are now impossible; keep error reporting in ext4_error_inode(). This prevents the underflow and the follow-on orphan/cleanup churn.

Affected products

• Linux Linux: before 5.4.301 (fixed in 5.4.301); before 5.10.246 (fixed in 5.10.246); before 5.15.195 (fixed in 5.15.195); before 6.1.157 (fixed in 6.1.157); before 6.6.113 (fixed in 6.6.113); before 6.12.54 (fixed in 6.12.54); …

Published 2025-11-12. Last modified 2026-07-30.