How severe is CVE-2025-21637?

CVE-2025-21637 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-2025-21637 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-21637?

CVE-2025-21637 primarily affects Linux Linux Kernel. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2025-21637?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-21637 have an EU (EUVD) identifier?

Yes. CVE-2025-21637 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-2586.

When was CVE-2025-21637 published?

CVE-2025-21637 was published on 2025-01-19 and last updated on 2026-06-17.

CVE-2025-21637

CVE-2025-21637 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

Severity: Medium (CVSS 3.x base score 5.5)
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-2586
Weakness: CWE-476
Affected product: Linux Linux Kernel
Published: 2025-01-19
Last modified: 2026-06-17

Description

In the Linux kernel, the following vulnerability has been resolved: sctp: sysctl: udp_port: avoid using current->nsproxy As mentioned in a previous commit of this series, using the 'net' structure via 'current' is not recommended for different reasons: - Inconsistency: getting info from the reader's/writer's netns vs only from the opener's netns. - current->nsproxy can be NULL in some cases, resulting in an 'Oops' (null-ptr-deref), e.g. when the current task is exiting, as spotted by syzbot [1] using acct(2). The 'net' structure can be obtained from the table->data using container_of(). Note that table->data could also be used directly, but that would increase the size of this fix, while 'sctp.ctl_sock' still needs to be retrieved from 'net' structure.

Frequently asked questions

What is CVE-2025-21637?: In the Linux kernel, the following vulnerability has been resolved: sctp: sysctl: udp_port: avoid using current->nsproxy As mentioned in a previous commit of this series, using the 'net' structure via 'current' is not recommended for different reasons: - Inconsistency: getting info from the reader's/writer's netns vs only from the opener's netns. - current->nsproxy can be NULL in some cases, resulting in an 'Oops' (null-ptr-deref), e.g. when the current task is exiting, as spotted by syzbot [1] using acct(2). The 'net' structure can be obtained from the table->data using container_of(). Note that table->data could also be used directly, but that would increase the size of this fix, while 'sctp.ctl_sock' still needs to be retrieved from 'net' structure.
How severe is CVE-2025-21637?: CVE-2025-21637 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-2025-21637 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-21637?: CVE-2025-21637 primarily affects Linux Linux Kernel. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-21637?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-21637 have an EU (EUVD) identifier?: Yes. CVE-2025-21637 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-2586.
When was CVE-2025-21637 published?: CVE-2025-21637 was published on 2025-01-19 and last updated on 2026-06-17.

References

Affected products (7)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc6:*:*:*:*:*:*

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