Bug 2555232 (CVE-2026-98837)

Summary:	CVE-2026-98837 kernel: ALSA: caiaq: unregister the input device when probe fails
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's ALSA caiaq USB audio driver. This flaw allows a local attacker to cause a Denial of Service (DoS) or potentially escalate privileges. When device initialization fails during the probing process, the driver frees internal device state structures while leaving the associated input device registered in the operating system. Accessing device attributes on this dangling input device subsequently triggers a use-after-free condition, leading to a system crash or kernel memory corruption.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-10-18 16:03:31 UTC

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

ALSA: caiaq: unregister the input device when probe fails

setup_card() registers the input device, whose name and phys point into
struct snd_usb_caiaqdev, and then goes on to snd_card_register() and
snd_usb_caiaq_control_init(). If either fails, snd_probe() calls
snd_card_free(), which frees the device state but leaves the input
device registered: card_free() only clears the pointer, and the input
device is unregistered from snd_disconnect() alone. Reading its "uevent"
attribute afterwards dereferences freed memory:

  BUG: KASAN: slab-use-after-free in string+0x4a9/0x4f0
  Read of size 1 at addr ffff8880208f5043 by task caiaq/4967
   add_uevent_var+0x183/0x3a0
   input_dev_uevent+0x162/0x900
   dev_uevent+0x2f1/0x870
   uevent_show+0x1ca/0x3a0
   ...

Unregister the input device on the probe error path, as
snd_disconnect() does. snd_usb_caiaq_input_disconnect() is a no-op when
no input device was registered.

Reproduced with a raw-gadget Audio Kontrol 1 and a temporary hack that
makes snd_usb_caiaq_control_init() fail.

Comment 1 Mauro Matteo Cascella 2026-10-23 21:24:59 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98837.mbox