Linux Kernel up to 6.18.5/6.19-rc3/6.19-rc4 ublk ublk_ctrl_start_dev use after free

Summaryinfo

A vulnerability categorized as critical has been discovered in Linux Kernel up to 6.18.5/6.19-rc3/6.19-rc4. The impacted element is the function ublk_ctrl_start_dev of the component ublk. Such manipulation leads to use after free. This vulnerability is uniquely identified as CVE-2026-22995. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.5/6.19-rc3/6.19-rc4. It has been rated as critical. Affected by this issue is the function ublk_ctrl_start_dev of the component ublk. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: ublk: fix use-after-free in ublk_partition_scan_work A race condition exists between the async partition scan work and device teardown that can lead to a use-after-free of ub->ub_disk: 1. ublk_ctrl_start_dev() schedules partition_scan_work after add_disk() 2. ublk_stop_dev() calls ublk_stop_dev_unlocked() which does: - del_gendisk(ub->ub_disk) - ublk_detach_disk() sets ub->ub_disk = NULL - put_disk() which may free the disk 3. The worker ublk_partition_scan_work() then dereferences ub->ub_disk leading to UAF Fix this by using ublk_get_disk()/ublk_put_disk() in the worker to hold a reference to the disk during the partition scan. The spinlock in ublk_get_disk() synchronizes with ublk_detach_disk() ensuring the worker either gets a valid reference or sees NULL and exits early. Also change flush_work() to cancel_work_sync() to avoid running the partition scan work unnecessarily when the disk is already detached.

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-22995 since 01/13/2026. The exploitation is known to be easy. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 03/27/2026).

The vulnerability scanner Nessus provides a plugin with the ID 296401 (Linux Distros Unpatched Vulnerability : CVE-2026-22995), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.18.6, 6.19-rc4 or 6.19-rc5 eliminates this vulnerability. Applying the patch 72e28774e9644c2bdbb4920842fbf77103a15a85/f0d385f6689f37a2828c686fb279121df006b4cb is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (296401) and CERT Bund (WID-SEC-2026-0215). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• RESF Rocky Linux
• Open Source Linux Kernel

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.19-rc1
• 6.19-rc2
• 6.19-rc3
• 6.19-rc4

License

• open-source

Website

• Vendor: https://www.kernel.org/

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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