CVE-2026-31596 ocfs2: handle invalid dinode in ocfs2_group_extend

Medium 5.5 Published 24 Apr 2026 Updated 14 Jun 2026

A local attacker can crash the Linux kernel by triggering a bug in the OCFS2 filesystem resize operation with a crafted filesystem image.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-31596?

CVE-2026-31596 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

ocfs2: handle invalid dinode in ocfs2_group_extend

[BUG] kernel BUG at fs/ocfs2/resize.c:308! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI RIP: 0010:ocfs2_group_extend+0x10aa/0x1ae0 fs/ocfs2/resize.c:308 Code: 8b8520ff ffff83f8 860f8580 030000e8 5cc3c1fe Call Trace: ... ocfs2_ioctl+0x175/0x6e0 fs/ocfs2/ioctl.c:869 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x197/0x1e0 fs/ioctl.c:583 x64_sys_call+0x1144/0x26a0 arch/x86/include/generated/asm/syscalls_64.h:17 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x93/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x76/0x7e ...

[CAUSE] ocfs2_group_extend() assumes that the global bitmap inode block returned from ocfs2_inode_lock() has already been validated and BUG_ONs when the signature is not a dinode. That assumption is too strong for crafted filesystems because the JBD2-managed buffer path can bypass structural validation and return an invalid dinode to the resize ioctl.

[FIX] Validate the dinode explicitly in ocfs2_group_extend(). If the global bitmap buffer does not contain a valid dinode, report filesystem corruption with ocfs2_error() and fail the resize operation instead of crashing the kernel.

Which versions are affected by CVE-2026-31596?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-31596?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-31596 being exploited?

There is no known exploitation of CVE-2026-31596 in the wild and no public exploit code.

All Linux kernel vulnerabilities

Sources

Also known as AZL-83684, BELL-CVE-2026-31596, DEBIAN-CVE-2026-31596, GHSA-hvjf-55rw-w8jm, ROOT-OS-DEBIAN-11-CVE-2026-31596, ROOT-OS-DEBIAN-12-CVE-2026-31596 and 3 more.