CVE-2025-21666

CVE-2025-21666 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-476.

Key facts

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.

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.
How severe is CVE-2025-21666?
CVE-2025-21666 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-21666 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (12th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-21666?
CVE-2025-21666 primarily affects Linux Linux Kernel. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-21666?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-21666 have an EU (EUVD) identifier?
Yes. CVE-2025-21666 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-2615.
When was CVE-2025-21666 published?
CVE-2025-21666 was published on 2025-01-31 and last updated on 2026-06-17.

References

Affected products (8)

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