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Review reviewHigh

CVE-2021-47259

Linux Linux, linux_kernel, linux kernel

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.

CVSS
7.8
EPSS
-
- percentile
CISA KEV
Not listed
Published
2024.05.22
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 7.8

Vulnerability overview

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 product and versions

Product
Linux Linux, linux_kernel, linux kernel
Affected versions
>= 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da < c7eab9e2d7b4e983ce280276fb920af649955897, >= 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da < 42c10b0db064e45f5c5ae7019bbf2168ffab766c, >= 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da < 3e3c7ebbfac152d08be75c92802a64a1f6471a15, >= 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da < c3b6cf64dfe4ef96e7341508d50d6998da7062c7, >= 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da < 72651c6579a25317a90536181d311c663d0329ab, >= 8dcbec6d20eb881ba368d0aebc3a8a678aebb1da < 476bdb04c501fc64bf3b8464ffddefc8dbe01577, >= 4.13, >= 8dcbec6d20eb < 476bdb04c501, >= 4.13 < 4.14.237, >= 4.15 < 4.19.195, >= 4.20 < 5.4.126, >= 5.5 < 5.10.44, >= 5.11 < 5.12.11, 5.13
Fixed versions
4.14.237, 4.19.195, 5.4.126, 5.10.44, 5.12.11

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux Linux, linux_kernel, linux kernel and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-416