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CVE-2021-4037: Kernel: security regression for cve-2018-13405

• Severity: medium (CVSS 4.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2022-08-24 · updated 2026-10-14
• Weakness: CWE-284

Description

A vulnerability was found in the fs/inode.c:inode_init_owner() function logic of the LInux kernel that allows local users to create files for the XFS file-system with an unintended group ownership and with group execution and SGID permission bits set, in a scenario where a directory is SGID and belongs to a certain group and is writable by a user who is not a member of this group. This can lead to excessive permissions granted in case when they should not. This vulnerability is similar to the previous CVE-2018-13405 and adds the missed fix for the XFS.

Affected products

• Debian Linux: 10.0, 11.0
• Linux kernel: before 5.11 — fixed in 5.11

How to fix

Upgrade to a fixed version: Linux kernel 5.11. Check the vendor advisory for mitigations.

References

• https://access.redhat.com/errata/RHSA-2022:1975
• https://access.redhat.com/errata/RHSA-2022:1988
• https://access.redhat.com/errata/RHSA-2022:4829
• https://access.redhat.com/errata/RHSA-2022:4835
• https://access.redhat.com/security/cve/CVE-2021-4037
• https://bugzilla.redhat.com/show_bug.cgi?id=2027239
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=01ea173e103e
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0fa3ecd87848
• https://access.redhat.com/security/cve/CVE-2021-4037
• https://bugzilla.redhat.com/show_bug.cgi?id=2004810
• https://bugzilla.redhat.com/show_bug.cgi?id=2027239
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=01ea173e103e

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