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CVE-2021-47634

7.8 · HIGH

In the Linux kernel, the following vulnerability has been resolved: ubi: Fix race condition between ctrl_cdev_ioctl and ubi_cdev_ioctl Hulk Robot reported a KASAN report about use-after-free: ==…

Published Feb 26, 2025CWE-416EPSS 0.29%

Overview

CVE-2021-47634 is a high-severity vulnerability. It was published on February 26, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

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

ubi: Fix race condition between ctrl_cdev_ioctl and ubi_cdev_ioctl

Hulk Robot reported a KASAN report about use-after-free:

==================================================================

BUG: KASAN: use-after-free in __list_del_entry_valid+0x13d/0x160

Read of size 8 at addr ffff888035e37d98 by task ubiattach/1385

[...]

Call Trace:

klist_dec_and_del+0xa7/0x4a0

klist_put+0xc7/0x1a0

device_del+0x4d4/0xed0

cdev_device_del+0x1a/0x80

ubi_attach_mtd_dev+0x2951/0x34b0 [ubi]

ctrl_cdev_ioctl+0x286/0x2f0 [ubi]

Allocated by task 1414:

device_add+0x60a/0x18b0

cdev_device_add+0x103/0x170

ubi_create_volume+0x1118/0x1a10 [ubi]

ubi_cdev_ioctl+0xb7f/0x1ba0 [ubi]

Freed by task 1385:

cdev_device_del+0x1a/0x80

ubi_remove_volume+0x438/0x6c0 [ubi]

ubi_cdev_ioctl+0xbf4/0x1ba0 [ubi]

[...]

==================================================================

The lock held by ctrl_cdev_ioctl is ubi_device

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/1a3f1cf87054833242fcd0218de0481cf855f888Refgit.kernel.org/stable/c/3cbf0e392f173ba0ce425968c8374a6aa3e90f2eRefgit.kernel.org/stable/c/432b057f8e847ae5a2306515606f8d2defaca178Refgit.kernel.org/stable/c/5f9e9c223e48c264241d2f34d0bfc29e5fcb5c1bRefgit.kernel.org/stable/c/a8ecee49259f8f78d91ddb329ab2be7e6fd01974Refgit.kernel.org/stable/c/c32fe764191b8ae8b128588beb96e3718d9179d8Refgit.kernel.org/stable/c/d727fd32cbd1abf3465f607021bc9c746f17b5a8Refgit.kernel.org/stable/c/f149b1bd213820363731aa119e5011ca892a2aac

How CyberStrike helps

Frequently asked questions

What is CVE-2021-47634?

CVE-2021-47634 is a high-severity vulnerability. It was published on February 26, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

How severe is CVE-2021-47634?

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2021-47634?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2021-47634?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-47634 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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