CVE-2026-53304 scsi: sg: Resolve soft lockup issue when opening /dev/sgX
A local attacker with root privileges can cause a kernel soft lockup by setting an invalid module parameter, leading to system unavailability.
- 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-2026-53304?
CVE-2026-53304 is a medium-severity denial of service vulnerability in Linux kernel, published on 26 Jun 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:
scsi: sg: Resolve soft lockup issue when opening /dev/sgX
The parameter def_reserved_size defines the default buffer size reserved for each Sg_fd and should be restricted to a range between 0 and 1,048,576 (see https://tldp.org/HOWTO/SCSI-Generic-HOWTO/proc.html). Although the function sg_proc_write_dressz enforces this limit, it is possible to bypass it by directly modifying the module parameter as shown below, which then causes a soft lockup:
echo -1 > /sys/module/sg/parameters/def_reserved_size exec 4<> /dev/sg0
watchdog: BUG: soft lockup - CPU#5 stuck for 26 seconds! [bash:537] Modules loaded: CPU: 5 UID: 0 PID: 537 Command: bash, kernel version 6.19.0-rc3+ #134, PREEMPT disabled Hardware: QEMU Standard PC (i440FX + PIIX, 1996), BIOS version 1.16.1-2.fc37 dated 04/01/2014 ... Call Trace:
sg_build_reserve+0x5c/0xa0 sg_add_sfp+0x168/0x270 sg_open+0x16e/0x340 chrdev_open+0xbe/0x230 do_dentry_open+0x175/0x480 vfs_open+0x34/0xf0 do_open+0x265/0x3d0 path_openat+0x110/0x290 do_filp_open+0xc3/0x170 do_sys_openat2+0x71/0xe0 __x64_sys_openat+0x6d/0xa0 do_syscall_64+0x62/0x310 entry_SYSCALL_64_after_hwframe+0x76/0x7e
The fix is to use module_param_cb to validate and reject invalid values assigned to def_reserved_size.
Weakness: CWE-667
Which versions are affected by CVE-2026-53304?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53304?
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-2026-53304 being exploited?
There is no known exploitation of CVE-2026-53304 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-53304, DEBIAN-CVE-2026-53304, GHSA-cx67-j66h-cm23, ROOT-OS-UBUNTU-2204-CVE-2026-53304, ROOT-OS-UBUNTU-2404-CVE-2026-53304, UBUNTU-CVE-2026-53304.