CVE-2025-21666: linux kernel Null Dereference — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: vsock: prevent null-ptr-deref in vsock_*[has_data|has_space] Recent reports have shown how we sometimes call vsock_*_has_data() when a vsock socket has been de-assigned from a transport (see attached links), but we shouldn't. Previous commits should have solved the real problems, but we may have more in the future, so to avoid null-ptr-deref, we can return 0 (no space, no data available) but with a warning. This way the code should continue to run in a nearly consistent state and have a warning that allows us to debug future problems.

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CVSS v3.1 Score

5.5

MEDIUM

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

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.5 — 5.15.177
linux	linux_kernel	5.16 — 6.1.127
linux	linux_kernel	6.2 — 6.6.74
linux	linux_kernel	6.7 — 6.12.11
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/91751e248256efc111e52e15115840c35d85abaf https://git.kernel.org/stable/c/9e5fed46ccd2c34c5fa5a9c8825ce4823fdc853e https://git.kernel.org/stable/c/b52e50dd4fabd12944172bd486a4f4853b7f74dd https://git.kernel.org/stable/c/bc9c49341f9728c31fe248c5fbba32d2e81a092b https://git.kernel.org/stable/c/c23d1d4f8efefb72258e9cedce29de10d057f8ca https://git.kernel.org/stable/c/daeac89cdb03d30028186f5ff7dc26ec8fa843e7

Other References

https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html https://cert-portal.siemens.com/productcert/html/ssa-265688.html

Frequently Asked Questions

What is CVE-2025-21666? +

In the Linux kernel, the following vulnerability has been resolved: vsock: prevent null-ptr-deref in vsock_*[has_data|has_space] Recent reports have shown how we sometimes call vsock_*_has_data() when a vsock socket has been de-assigned from a transport (see attached links), but we shouldn't. Previous commits should have solved the real problems, but we may have more in the future, so to avoid null-ptr-deref, we can return 0 (no space, no data available) but with a warning. This way the code should continue to run in a nearly consistent state and have a warning that allows us to debug future problems. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-21666? +

CVE-2025-21666 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-21666? +

CVE-2025-21666 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-21666? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2025-21666