CVE-2021-33909
kernel: size_t-to-int conversion vulnerability in the filesystem layer
Severity
ImportantRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · July 20, 2021
Updated · August 7, 2026
Description
An out-of-bounds write flaw was found in the Linux kernel's seq_file in the Filesystem layer. This flaw allows a local attacker with a user privilege to gain access to out-of-bound memory, leading to a system crash, leak of internal kernel information and can escalate privileges. The issue results from not validating the size_t-to-int conversion prior to performing operations. The highest threat from this vulnerability is to data integrity, confidentiality and system availability.
Statement
Any Red Hat product which relies on the Red Hat Enterprise Linux kernel is also potentially impacted. This includes layered products such as OpenShift Container Platform, OpenStack, Red Hat Virtualization, and others.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.
CVSS / CWE
CVSS 3.1 · 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS 3.1 · 6.7CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
CWE-787 · Out-of-bounds Write