Is CVE-2026-52909 in the CISA KEV catalog?

No. CVE-2026-52909 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-52909?

CVE-2026-52909 has a CVSS v3 base score of 7.8 (Important).

What is the EPSS score for CVE-2026-52909?

CVE-2026-52909 has an EPSS score of 0.12% (2th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-52909?

Upgrade linux on debian 11 to 5.10.259-1 or later.

CVE & CISA-KEV Catalog

CVE-2026-52909

HIGH

7.8

CVSS v3

NVD

Description

In the Linux kernel, the following vulnerability has been resolved: ip6_vti: set netns_immutable on the fallback device. john1988 and Noam Rathaus reported that vti6_init_net() does not set the netns_immutable flag on the per-netns fallback tunnel device (ip6_vti0). Other similar tunnel drivers (like ip6_tunnel, sit, ip6_gre, and ip_tunnel) correctly set this flag during their fallback device initialization to prevent them from being moved to another network namespace.

How to fix

Remediation Available

linuxDebian

Fixed in:5.10.259-1CVE-2026-52909

Fixed in:6.1.176-1CVE-2026-52909

Fixed in:6.12.94-1CVE-2026-52909

Fixed in:7.0.13-1CVE-2026-52909

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorLocal

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

0.12%probability of exploitation in 30 days

2ndpercentile

Low risk: more likely to be exploited than 2% of all known CVEs.

References

Other references8

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-04.