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CVE-2021-47507

4.7 · MEDIUM

In the Linux kernel, the following vulnerability has been resolved: nfsd: Fix nsfd startup race (again) Commit bd5ae9288d64 ("nfsd: register pernet ops last, unregister first") has re-opened rpc_…

Published May 24, 2024CWE-362EPSS 0.19%

Overview

CVE-2021-47507 is a medium-severity vulnerability. It was published on May 24, 2024 and has a CVSS 3.1 base score of 4.7 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 4.7, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

In the Linux kernel, the following vulnerability has been resolved:

nfsd: Fix nsfd startup race (again)

Commit bd5ae9288d64 ("nfsd: register pernet ops last, unregister first")

has re-opened rpc_pipefs_event() race against nfsd_net_id registration

(register_pernet_subsys()) which has been fixed by commit bb7ffbf29e76

("nfsd: fix nsfd startup race triggering BUG_ON").

Restore the order of register_pernet_subsys() vs register_cld_notifier().

Add WARN_ON() to prevent a future regression.

Crash info:

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000012

CPU: 8 PID: 345 Comm: mount Not tainted 5.4.144-... #1

pc : rpc_pipefs_event+0x54/0x120 [nfsd]

lr : rpc_pipefs_event+0x48/0x120 [nfsd]

Call trace:

rpc_pipefs_event+0x54/0x120 [nfsd]

blocking_notifier_call_chain

rpc_fill_super

get_tree_keyed

rpc_fs_get_tree

vfs_get_tree

do_mount

ksys_mount

__arm64_sys_mount

el0_svc_handler

el0_svc

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/8bf902fee5893cfc2f04a698abab47629699ae9aRefgit.kernel.org/stable/c/b10252c7ae9c9d7c90552f88b544a44ee773af64Refgit.kernel.org/stable/c/c520943a00ad5015704969ad3304c956bcd49d25Refgit.kernel.org/stable/c/f5734b1714ca355703e9ea8fb61d04beff1790b9Refgit.kernel.org/stable/c/8bf902fee5893cfc2f04a698abab47629699ae9aRefgit.kernel.org/stable/c/b10252c7ae9c9d7c90552f88b544a44ee773af64Refgit.kernel.org/stable/c/c520943a00ad5015704969ad3304c956bcd49d25Refgit.kernel.org/stable/c/f5734b1714ca355703e9ea8fb61d04beff1790b9

How CyberStrike helps

Frequently asked questions

What is CVE-2021-47507?

CVE-2021-47507 is a medium-severity vulnerability. It was published on May 24, 2024 and has a CVSS 3.1 base score of 4.7 (MEDIUM).

How severe is CVE-2021-47507?

This vulnerability has a CVSS 3.1 base score of 4.7, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2021-47507?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2021-47507?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-47507 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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