CVE-2023-53485 fs: jfs: Fix UBSAN: array-index-out-of-bounds in dbAllocDmapLev

High 7.8 Published 1 Oct 2025 Updated 5 Aug 2026

A local attacker can trigger an out-of-bounds array index in the JFS filesystem, causing a kernel crash and denial of service.

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-2023-53485?

CVE-2023-53485 is a high-severity vulnerability in Linux kernel, published on 1 Oct 2025. 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:

fs: jfs: Fix UBSAN: array-index-out-of-bounds in dbAllocDmapLev

Syzkaller reported the following issue:

UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dmap.c:1965:6 index -84 is out of range for type 's8[341]' (aka 'signed char[341]') CPU: 1 PID: 4995 Comm: syz-executor146 Not tainted 6.4.0-rc6-syzkaller-00037-gb6dad5178cea #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106 ubsan_epilogue lib/ubsan.c:217 [inline] __ubsan_handle_out_of_bounds+0x11c/0x150 lib/ubsan.c:348 dbAllocDmapLev+0x3e5/0x430 fs/jfs/jfs_dmap.c:1965 dbAllocCtl+0x113/0x920 fs/jfs/jfs_dmap.c:1809 dbAllocAG+0x28f/0x10b0 fs/jfs/jfs_dmap.c:1350 dbAlloc+0x658/0xca0 fs/jfs/jfs_dmap.c:874 dtSplitUp fs/jfs/jfs_dtree.c:974 [inline] dtInsert+0xda7/0x6b00 fs/jfs/jfs_dtree.c:863 jfs_create+0x7b6/0xbb0 fs/jfs/namei.c:137 lookup_open fs/namei.c:3492 [inline] open_last_lookups fs/namei.c:3560 [inline] path_openat+0x13df/0x3170 fs/namei.c:3788 do_filp_open+0x234/0x490 fs/namei.c:3818 do_sys_openat2+0x13f/0x500 fs/open.c:1356 do_sys_open fs/open.c:1372 [inline] __do_sys_openat fs/open.c:1388 [inline] __se_sys_openat fs/open.c:1383 [inline] __x64_sys_openat+0x247/0x290 fs/open.c:1383 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f1f4e33f7e9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffc21129578 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f1f4e33f7e9 RDX: 000000000000275a RSI: 0000000020000040 RDI: 00000000ffffff9c RBP: 00007f1f4e2ff080 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f1f4e2ff110 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 </TASK>

The bug occurs when the dbAllocDmapLev()function attempts to access dp->tree.stree[leafidx + LEAFIND] while the leafidx value is negative.

To rectify this, the patch introduces a safeguard within the dbAllocDmapLev() function. A check has been added to verify if leafidx is negative. If it is, the function immediately returns an I/O error, preventing any further execution that could potentially cause harm.

Tested via syzbot.

Weakness: CWE-129

Which versions are affected by CVE-2023-53485?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2023-53485?

Apply the vendor's patch.

Is CVE-2023-53485 being exploited?

There is no known exploitation of CVE-2023-53485 in the wild and no public exploit code.

All Linux kernel vulnerabilities

Sources

Also known as BELL-CVE-2023-53485, DEBIAN-CVE-2023-53485, GHSA-hvxw-2j3f-v3hp, UBUNTU-CVE-2023-53485.