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CVE-2021-47418

5.5 · MEDIUM

In the Linux kernel, the following vulnerability has been resolved: net_sched: fix NULL deref in fifo_set_limit() syzbot reported another NULL deref in fifo_set_limit() [1] I could repro the iss…

Published May 21, 2024CWE-476EPSS 0.23%

Overview

CVE-2021-47418 is a medium-severity vulnerability. It was published on May 21, 2024 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.5, 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:

net_sched: fix NULL deref in fifo_set_limit()

syzbot reported another NULL deref in fifo_set_limit() [1]

I could repro the issue with :

unshare -n

tc qd add dev lo root handle 1:0 tbf limit 200000 burst 70000 rate 100Mbit

tc qd replace dev lo parent 1:0 pfifo_fast

tc qd change dev lo root handle 1:0 tbf limit 300000 burst 70000 rate 100Mbit

pfifo_fast does not have a change() operation.

Make fifo_set_limit() more robust about this.

[1]

BUG: kernel NULL pointer dereference, address: 0000000000000000

PGD 1cf99067 P4D 1cf99067 PUD 7ca49067 PMD 0

Oops: 0010 [#1] PREEMPT SMP KASAN

CPU: 1 PID: 14443 Comm: syz-executor959 Not tainted 5.15.0-rc3-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

RIP: 0010:0x0

Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.

RSP: 0018:ffffc9000e2f7310 EFLAGS: 00010246

RAX: dffffc0000000000 RBX: ffffffff8d6ecc00 RCX: 0000000

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/08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4Refgit.kernel.org/stable/c/0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52Refgit.kernel.org/stable/c/26af64d71b6277841285fa40e3f7164a378dfda9Refgit.kernel.org/stable/c/560ee196fe9e5037e5015e2cdb14b3aecb1cd7dcRefgit.kernel.org/stable/c/acff2d182c0768a713cee77442caeb07668bd68fRefgit.kernel.org/stable/c/c951a3be5e8803e93bb49a0aca0d30457d3c1b67Refgit.kernel.org/stable/c/d07098f45be868a9cdce6c616563c36c64dbbd87Refgit.kernel.org/stable/c/fb58cd7991747b5e0b110c98c922d7b0e47a1f14Refgit.kernel.org/stable/c/08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4Refgit.kernel.org/stable/c/0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52

How CyberStrike helps

Frequently asked questions

What is CVE-2021-47418?

CVE-2021-47418 is a medium-severity vulnerability. It was published on May 21, 2024 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-47418?

This vulnerability has a CVSS 3.1 base score of 5.5, 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-2021-47418?

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-2021-47418?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-47418 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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