CVE-2026-90263
UnknownSummary
In the Linux kernel, in the btrfs filesystem, POSIX ACLs can be set even when the root has the read-only property set. The set_acl code path does not check the root's read-only flag because the relevant check was removed in commit 353c2ea735e4.
Risk Assessment
The ability to modify ACLs on a filesystem marked read-only violates expected security and data integrity guarantees. It may allow unauthorized changes to access permissions.
Recommendation
Update the Linux kernel to a version that checks the root's read-only flag before the set_acl operation. Until then, do not rely solely on the btrfs read-only property as a protection mechanism.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: btrfs: check if root is readonly when setting posix acl For a filesystem which has btrfs read-only property set to true, all write operations including acl and xattr should be denied. However, acl can still be set even if btrfs ro property is true. This happens because no function on the set_acl code path checks the root is readonly or not. It was checked in btrfs_setxattr_trans() but got removed in commit 353c2ea735e4 ("btrfs: remove redundant readonly root check in btrfs_setxattr_trans") That commit didn't check if all the callers properly check the root's read-only flag. A previous fix is commit b51111271b03 ("btrfs: check if root is readonly while setting security xattr"). Always check if the root is read-only before performing the set acl operation.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

