CVE-2026-53304 [Medium] | Security Bypass in Linux Kernel

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.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-27	—	0.18%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-27

—

0.18%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.5	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.8	3.6	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.5

3.1

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.8

3.6

[email protected]

OS Trackers for CVE-2026-53304

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2026-53304 not yet assigned priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6.	https://security-tracker.debian.org/tracker/CVE-2026-53304
`suse`	—	—	https://www.suse.com/security/cve/CVE-2026-53304/
`ubuntu`	medium	CVE-2026-53304 medium priority: Ubuntu including 162 source packages (linux, linux-allwinner-5.19, …), 1458 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): DNE 1051, ignored 176, needed 93, released 88, pending 49, needs-triage 1.	https://ubuntu.com/security/CVE-2026-53304

Affected software / configurations for CVE-2026-53304

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 2.6.19, < 5.10.258	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.11, < 5.15.209	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.16, < 6.1.175	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.2, < 6.6.141	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.7, < 6.12.91	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.13, < 6.18.33	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.19, < 7.0.10	cpe:2.3:o:linux:linux_kernel::::::::

References for CVE-2026-53304

URL	Tags
https://git.kernel.org/stable/c/1afd963fcd963db0dc5d47df6dfcf010c9c4647e	Patch
https://git.kernel.org/stable/c/3d74e0654ac908c65a8f20373091826fe43b1363	Patch
https://git.kernel.org/stable/c/9676ca7b1ef31a3a65b3e61e7ce3b54ce7364202	Patch
https://git.kernel.org/stable/c/c47ccfb3d80dfed522ca06a5954ac97488d78c5a	Patch
https://git.kernel.org/stable/c/c5f4a211e82d04ccc1809311322c47023bbe66e2	Patch
https://git.kernel.org/stable/c/d06a310b45e153872033dd0cf19d5a2279121099	Patch
https://git.kernel.org/stable/c/fe671d3c84ffb1b763d590c25195755adeaadaba	Patch
https://git.kernel.org/stable/c/feade299e932967de27519338d41de348fb5b061	Patch

URL

CVE-2026-53304 | scsi: sg: Resolve soft lockup issue when opening /dev/sgX

Exploit prediction scoring system (EPSS) score for CVE-2026-53304

Common vulnerability scoring system (CVSS) metrics for CVE-2026-53304

Weakness enumeration for CVE-2026-53304

GitHub Security Advisory for CVE-2026-53304

OS Trackers for CVE-2026-53304

Affected software / configurations for CVE-2026-53304

References for CVE-2026-53304