CVE-2025-39965: xfrm: xfrm_alloc_spi shouldn't use 0 as SPI

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-10-13 · updated 2026-10-30

Description

In the Linux kernel, the following vulnerability has been resolved: xfrm: xfrm_alloc_spi shouldn't use 0 as SPI x->id.spi == 0 means "no SPI assigned", but since commit 94f39804d891 ("xfrm: Duplicate SPI Handling"), we now create states and add them to the byspi list with this value. __xfrm_state_delete doesn't remove those states from the byspi list, since they shouldn't be there, and this shows up as a UAF the next time we go through the byspi list.

Affected products

Linux kernel: from 6.6.103 before 6.6.109; from 6.12.43 before 6.12.50; from 6.15.11 before 6.16; from 6.16.2 before 6.16.10; 6.17-rc1, 6.17-rc2, 6.17-rc3, 6.17-rc4, 6.17-rc5, 6.17-rc6 (+1) — fixed in 6.6.109, 6.12.50, 6.16, 6.16.10
Linux: from 6.1.191 before 6.2; from 6.15.11 before 6.16 — fixed in 6.2, 6.16

How to fix

Upgrade to a fixed version: Linux kernel 6.6.109, 6.12.50, 6.16, 6.16.10; Linux 6.2, 6.16. Check the vendor advisory for mitigations.

References

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