CVE-2021-47259: NFS: Fix use-after-free in nfs4_init_client()

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-05-21 · updated 2026-08-04
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: NFS: Fix use-after-free in nfs4_init_client() KASAN reports a use-after-free when attempting to mount two different exports through two different NICs that belong to the same server. Olga was able to hit this with kernels starting somewhere between 5.7 and 5.10, but I traced the patch that introduced the clear_bit() call to 4.13. So something must have changed in the refcounting of the clp pointer to make this call to nfs_put_client() the very last one.

Affected products

Linux kernel: from 4.13 before 4.14.237; from 4.15 before 4.19.195; from 4.20 before 5.4.126; from 5.5 before 5.10.44; from 5.11 before 5.12.11; 5.13-rc1, 5.13-rc2, 5.13-rc3, 5.13-rc4, 5.13-rc5 — fixed in 4.14.237, 4.19.195, 5.10.44, 5.12.11, 5.4.126

How to fix

Upgrade to a fixed version: Linux kernel 4.14.237, 4.19.195, 5.10.44, 5.12.11. Check the vendor advisory for mitigations.

References

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