Linux F2FS: Three Integrity and Validation Vulnerabilities Disclosed Together
Three vulnerabilities affecting the Linux kernel's F2FS file system were disclosed on July 20, 2026, related to data integrity and validation.
Key findings
- Three F2FS vulnerabilities in the Linux kernel were disclosed on July 20, 2026.
- CVE-2026-63819 involves an invalid opcode kernel BUG in f2fs node handling.
- CVE-2026-63814 addresses improper ACL entry size validation.
- CVE-2026-63815 relates to incorrect bounding of inline extended attribute sizes.
- All issues have been resolved in the Linux kernel.
On July 20, 2026, three vulnerabilities were disclosed in the Linux kernel's F2FS (Flash-Friendly File System) implementation, all reported on the same day. These issues, identified as CVE-2026-63819, CVE-2026-63814, and CVE-2026-63815, highlight potential weaknesses in file system integrity and data handling.
CVE-2026-63819 addresses a critical bug within the f2fs_get_node_folio_ra() function in fs/f2fs/file.c. The vulnerability manifests as an "invalid opcode" kernel BUG, indicating a severe execution flow error. This specific issue was detected by the syzkaller fuzzer, suggesting it could be triggered by malformed input or unexpected system states.
CVE-2026-63814 focuses on the validation of Access Control List (ACL) entry sizes within the f2fs_acl_from_disk() function. While f2fs_acl_count() checks the aggregate ACL extended attribute length, a malformed ACL could still lead to issues by placing ACL_USER or ACL_GROUP entries into slots that only contain struct f2fs_acl_entry_short data, potentially corrupting ACL information.
CVE-2026-63815 tackles an issue related to inode extended attribute sizes when the flexible_inline_xattr feature is enabled. The vulnerability lies in do_read_inode(), which unconditionally loads the on-disk i_inline_xattr_size. This could lead to incorrect size bounds for non-inline extended attributes on inodes, potentially causing data corruption or unexpected behavior.
All three vulnerabilities were resolved in the Linux kernel. Users are advised to update to patched versions of the kernel to mitigate these risks. The timely disclosure and resolution of these F2FS-related issues are crucial for maintaining the stability and security of file systems on flash storage devices.