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CVE-2021-47593

5.5 · MEDIUM

In the Linux kernel, the following vulnerability has been resolved: mptcp: clear 'kern' flag from fallback sockets The mptcp ULP extension relies on sk->sk_sock_kern being set correctly: It preve…

Published Jun 19, 2024CWE-476EPSS 0.25%

Overview

CVE-2021-47593 is a medium-severity vulnerability. It was published on June 19, 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:

mptcp: clear 'kern' flag from fallback sockets

The mptcp ULP extension relies on sk->sk_sock_kern being set correctly:

It prevents setsockopt(fd, IPPROTO_TCP, TCP_ULP, "mptcp", 6); from

working for plain tcp sockets (any userspace-exposed socket).

But in case of fallback, accept() can return a plain tcp sk.

In such case, sk is still tagged as 'kernel' and setsockopt will work.

This will crash the kernel, The subflow extension has a NULL ctx->conn

mptcp socket:

BUG: KASAN: null-ptr-deref in subflow_data_ready+0x181/0x2b0

Call Trace:

tcp_data_ready+0xf8/0x370

[..]

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/451f1eded7f56e93aaf52eb547ba97742d9c0e97Refgit.kernel.org/stable/c/c26ac0ea3a91c210cf90452e625dc441adf3e549Refgit.kernel.org/stable/c/d6692b3b97bdc165d150f4c1505751a323a80717Refgit.kernel.org/stable/c/451f1eded7f56e93aaf52eb547ba97742d9c0e97Refgit.kernel.org/stable/c/c26ac0ea3a91c210cf90452e625dc441adf3e549Refgit.kernel.org/stable/c/d6692b3b97bdc165d150f4c1505751a323a80717

How CyberStrike helps

Frequently asked questions

What is CVE-2021-47593?

CVE-2021-47593 is a medium-severity vulnerability. It was published on June 19, 2024 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-47593?

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-2021-47593?

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-2021-47593?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-47593 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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