CVE-2022-50747: 
Linux Kernel vulnerability analysis and mitigation

CVE-2022-50747 is an out-of-bounds (OOB) write vulnerability in the Linux kernel's HFS (Hierarchical File System) filesystem driver, specifically in the hfs_asc2mac function in fs/hfs/trans.c. The flaw was discovered via Syzbot fuzzing and disclosed on December 24, 2025. It affects Linux kernel versions from 2.6.14 up to the patched stable releases across multiple long-term support branches. The CVSS estimate is Medium severity, with an EPSS score of approximately 0.033% (Red Hat CVE, Feedly).

The root cause is a missing bounds check (CWE-787: Out-of-Bounds Write) in the hfs_asc2mac() function, which converts ASCII filenames to Mac format. When the input filename length (in->len) exceeds HFS_NAMELEN (31 characters — the maximum HFS filename length), the function continues writing to the destination buffer past its allocated boundary. The call chain triggering the bug is: hfs_lookup → hfs_cat_build_key → hfs_asc2mac, meaning the vulnerability can be reached when a process attempts to open a file on a mounted HFS filesystem with a crafted, oversized filename. KASAN reports this as a slab-out-of-bounds write of size 1. The fix adds a dstlen check inside the while() loop before each write to the destination address (Red Hat CVE, Red Hat Bugzilla).

Successful exploitation could result in kernel memory corruption due to the slab-out-of-bounds write, potentially leading to arbitrary code execution in kernel context or a kernel panic (system crash), impacting availability and integrity. An attacker with the ability to mount a crafted HFS filesystem image or influence filename processing on a system with HFS support enabled could trigger this condition. The vulnerability is local in nature and primarily affects systems that mount HFS filesystems, such as Linux systems interoperating with legacy Apple HFS volumes (Red Hat CVE, Feedly).

Patches have been backported to multiple Linux stable kernel branches. Fixed versions include: 4.9.337, 4.14.303, 4.19.270, 5.4.229, 5.10.163, 5.15.86, 6.0.16, 6.1.2, and 6.2. Administrators should update to the latest patched kernel version for their distribution. As a workaround, systems that do not require HFS filesystem support can blacklist or disable the hfs kernel module (echo 'install hfs /bin/true' >> /etc/modprobe.d/disable-hfs.conf) to prevent the vulnerable code path from being reached (Red Hat CVE, Red Hat Bugzilla).