PT-2021-8082 · Linux+4 · Linux Kernel+4
Vincent Pelletier
·
Published
2021-12-21
·
Updated
2024-08-19
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CVE-2021-46933
CVSS v3.1
5.5
Medium
| Vector | AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
Name of the Vulnerable Software and Affected Versions
Linux kernel versions prior to 5.15.3-1
Description
The vulnerability is related to a refcount underflow in the
ffs data clear function of the usb f fs module. When userland closes ep0 and then unmounts f fs, ffs data clear is indirectly called twice, causing eventfd ctx put to be called multiple times and resulting in a refcount underflow. This can lead to a use-after-free error. The issue is resolved by NULL-ifying ffs eventfd to prevent extraneous eventfd ctx put calls.Recommendations
To resolve the issue, update the Linux kernel to version 5.15.3-1 or later. As a temporary workaround, consider disabling the
ffs data clear function until a patch is available. However, this may have unintended consequences and should be used with caution.Note: The provided information does not specify the exact versions affected, but based on the data, it appears that versions prior to 5.15.3-1 are vulnerable.
Exploit
Fix
NULL Pointer Dereference
Use After Free
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Related Identifiers
Affected Products
Astra Linux
Linux Kernel
Red Os
Suse
Ubuntu