CVE-2026-31726 [Medium] | Use-After-Free in Linux Kernel

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: uvc: fix NULL pointer dereference during unbind race Commit b81ac4395bbe ("usb: gadget: uvc: allow for application to cleanly shutdown") introduced two stages of synchronization waits totaling 1500ms in uvc_function_unbind() to prevent several types of kernel panics. However, this timing-based approach is insufficient during power management (PM) transitions. When the PM subsystem starts freezing user space processes, the wait_event_interruptible_timeout() is aborted early, which allows the unbind thread to proceed and nullify the gadget pointer (cdev->gadget = NULL): [ 814.123447][ T947] configfs-gadget.g1 gadget.0: uvc: uvc_function_unbind() [ 814.178583][ T3173] PM: suspend entry (deep) [ 814.192487][ T3173] Freezing user space processes [ 814.197668][ T947] configfs-gadget.g1 gadget.0: uvc: uvc_function_unbind no clean disconnect, wait for release When the PM subsystem resumes or aborts the suspend and tasks are restarted, the V4L2 release path is executed and attempts to access the already nullified gadget pointer, triggering a kernel panic: [ 814.292597][ C0] PM: pm_system_irq_wakeup: 479 triggered dhdpcie_host_wake [ 814.386727][ T3173] Restarting tasks ... [ 814.403522][ T4558] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000030 [ 814.404021][ T4558] pc : usb_gadget_deactivate+0x14/0xf4 [ 814.404031][ T4558] lr : usb_function_deactivate+0x54/0x94 [ 814.404078][ T4558] Call trace: [ 814.404080][ T4558] usb_gadget_deactivate+0x14/0xf4 [ 814.404083][ T4558] usb_function_deactivate+0x54/0x94 [ 814.404087][ T4558] uvc_function_disconnect+0x1c/0x5c [ 814.404092][ T4558] uvc_v4l2_release+0x44/0xac [ 814.404095][ T4558] v4l2_release+0xcc/0x130 Address the race condition and NULL pointer dereference by: 1. State Synchronization (flag + mutex) Introduce a 'func_unbound' flag in struct uvc_device. This allows uvc_function_disconnect() to safely skip accessing the nullified cdev->gadget pointer. As suggested by Alan Stern, this flag is protected by a new mutex (uvc->lock) to ensure proper memory ordering and prevent instruction reordering or speculative loads. This mutex is also used to protect 'func_connected' for consistent state management. 2. Explicit Synchronization (completion) Use a completion to synchronize uvc_function_unbind() with the uvc_vdev_release() callback. This prevents Use-After-Free (UAF) by ensuring struct uvc_device is freed after all video device resources are released.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-02	—	0.02%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-02

—

0.02%

—

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-2026-31726

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2026-31726 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-2026-31726
`redhat`	—	—	https://access.redhat.com/security/cve/CVE-2026-31726
`suse`	medium	CVE-2026-31726 severity moderate: SUSE including 20 source package names (cluster-md-kmp-default, dlm-kmp-default, …), 104 product×package rows across 24 product lines (SUSE Linux Enterprise High Availability Extension 15 SP7, SUSE Linux Enterprise Live Patching 12 SP5, … (24 product lines)): Known Not Affected 104.	https://www.suse.com/security/cve/CVE-2026-31726/
`ubuntu`	medium	CVE-2026-31726 medium priority: Ubuntu including 161 source packages (linux, linux-allwinner-5.19, …), 1449 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): DNE 1047, ignored 169, needed 89, released 84, not-affected 55, needs-triage 5.	https://ubuntu.com/security/CVE-2026-31726

Affected software / configurations for CVE-2026-31726

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 5.10.117, < 5.10.253	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.15.41, < 5.15.203	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.18, < 6.1.168	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.2, < 6.6.134	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.7, < 6.12.81	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.13, < 6.18.22	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.19, < 6.19.12	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	7.0	cpe:2.3:o:linux:linux_kernel:7.0:rc1::::::
linux	linux_kernel	7.0	cpe:2.3:o:linux:linux_kernel:7.0:rc2::::::
linux	linux_kernel	7.0	cpe:2.3:o:linux:linux_kernel:7.0:rc3::::::
linux	linux_kernel	7.0	cpe:2.3:o:linux:linux_kernel:7.0:rc4::::::
linux	linux_kernel	7.0	cpe:2.3:o:linux:linux_kernel:7.0:rc5::::::
linux	linux_kernel	7.0	cpe:2.3:o:linux:linux_kernel:7.0:rc6::::::

References for CVE-2026-31726

URL	Tags
https://git.kernel.org/stable/c/0587de744615628c38e33ddc1601160a5ea8c50a	Patch
https://git.kernel.org/stable/c/0c00ec409d7b2bce3fcac73188b79a141db7cfda	Patch
https://git.kernel.org/stable/c/1aa9356881ee4ed414bf72d0c56d915492cb5345	Patch
https://git.kernel.org/stable/c/8a1128d604c360eca135f15b882b70256a522145	Patch
https://git.kernel.org/stable/c/c038ba56b92e410d1caec22b2dc68780a0b42091	Patch
https://git.kernel.org/stable/c/c78e463ee134b4669579d453c81ae00795e4c19a	Patch
https://git.kernel.org/stable/c/d92d1532e05b1b31d36d48765e43bf73d793d19f	Patch
https://git.kernel.org/stable/c/eba2936bbe6b752a31725a9eb5c674ecbf21ee7d	Patch

URL

CVE-2026-31726 | usb: gadget: uvc: fix NULL pointer dereference during unbind race

Exploit prediction scoring system (EPSS) score for CVE-2026-31726

Common vulnerability scoring system (CVSS) metrics for CVE-2026-31726

Weakness enumeration for CVE-2026-31726

GitHub Security Advisory for CVE-2026-31726

OS Trackers for CVE-2026-31726

Affected software / configurations for CVE-2026-31726

References for CVE-2026-31726