CVE-2024-42318: landlock: Don't lose track of restrictions on cred_transfer

Severity: medium (CVSS 5.5 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: 2024-08-17 · updated 2026-08-04

Description

In the Linux kernel, the following vulnerability has been resolved: landlock: Don't lose track of restrictions on cred_transfer When a process' cred struct is replaced, this _almost_ always invokes the cred_prepare LSM hook; but in one special case (when KEYCTL_SESSION_TO_PARENT updates the parent's credentials), the cred_transfer LSM hook is used instead. Landlock only implements the cred_prepare hook, not cred_transfer, so KEYCTL_SESSION_TO_PARENT causes all information on Landlock restrictions to be lost. This basically means that a process with the ability to use the fork() and keyctl() syscalls can get rid of all Landlock restrictions on itself. Fix it by adding a cred_transfer hook that does the same thing as the existing cred_prepare hook. (Implemented by having hook_cred_prepare() call hook_cred_transfer() so that the two functions are less likely to accidentally diverge in the future.)

Affected products

Linux kernel: from 5.13 before 5.15.165; from 5.16 before 6.1.103; from 6.2 before 6.6.44; from 6.7 before 6.10.3 — fixed in 5.15.165, 6.1.103, 6.10.3, 6.6.44

How to fix

Upgrade to a fixed version: Linux kernel 5.15.165, 6.1.103, 6.10.3, 6.6.44. Check the vendor advisory for mitigations.

References

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