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Vulnerability record · CVE-2021-38209 · published 8 August 2021

CVE-2021-38209: Linux kernel observable discrepancy vulnerability

Linux · Linux Kernel

net/netfilter/nf_conntrack_standalone.c in the Linux kernel before 5.12.2 allows observation of changes in any net namespace because these changes are leaked into all other net namespaces. This is related to the NF_SYSCTL_CT_MAX, NF_SYSCTL_CT_EXPECT_MAX, and NF_SYSCTL_CT_BUCKETS sysctls.

3.3 CVSS 3.1 Low EPSS 0.28% · top 81.3% CWE-203 · Observable discrepancy
3.3CVSS 3.1 base score, v2 2.1
0.28%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

Description

net/netfilter/nf_conntrack_standalone.c in the Linux kernel before 5.12.2 allows observation of changes in any net namespace because these changes are leaked into all other net namespaces. This is related to the NF_SYSCTL_CT_MAX, NF_SYSCTL_CT_EXPECT_MAX, and NF_SYSCTL_CT_BUCKETS sysctls.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.12.2 Mailing ListPatchVendor Advisory
https://github.com/torvalds/linux/commit/2671fa4dc0109d3fb581bc3078fdf17b5d9080f6 PatchThird Party Advisory
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.12.2 Mailing ListPatchVendor Advisory
https://github.com/torvalds/linux/commit/2671fa4dc0109d3fb581bc3078fdf17b5d9080f6 PatchThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-38209), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.