Linux Kernel xfrm6_fill_dst: Double netdev_put refcount underflow
CVE-2026-64580 Published on August 5, 2026
xfrm6: clear dst.dev on error to avoid double netdev_put in xfrm6_fill_dst()
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
...
Products Associated with CVE-2026-64580
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Affected Versions
Linux:- Version 84c4a9dfbf430861e7588d95ae3ff61535dca351 and below df6856c2dda9187601d29b5fbd7a81b3b178cedf is affected.
- Version 84c4a9dfbf430861e7588d95ae3ff61535dca351 and below 43de8a49335e611adb271bbd52e84dfbc11fc185 is affected.
- Version 84c4a9dfbf430861e7588d95ae3ff61535dca351 and below ff636d7b7cba6dea82ecf580415ea57f2c1a11b6 is affected.
- Version 84c4a9dfbf430861e7588d95ae3ff61535dca351 and below e078da1b4e11390cff3201c19a9a1fe70c5b934f is affected.
- Version 84c4a9dfbf430861e7588d95ae3ff61535dca351 and below 136992de9bb91871084ae52d172610541c76e4d2 is affected.
- Version a7e22d0c0e81dde129a51ee413644124f4b59954 is affected.
- Version 01b0d887f67a388fb2a658ee2bdd74e5ba146818 is affected.
- Version a98124aac0b5adc5de8ae54f11322781cb4d85c3 is affected.
- Version e27b7bee743d921f037b1da6f071237345bef7c1 is affected.
- Version 3.0.79 and below 3.1 is affected.
- Version 3.2.46 and below 3.3 is affected.
- Version 3.4.46 and below 3.5 is affected.
- Version 3.9.3 and below 3.10 is affected.
- Version 3.10 is affected.
- Before 3.10 is unaffected.
- Version 6.6.148, <= 6.6.* is unaffected.
- Version 6.12.101, <= 6.12.* is unaffected.
- Version 6.18.42, <= 6.18.* is unaffected.
- Version 7.1.6, <= 7.1.* is unaffected.
- Version 7.2-rc4, <= * is unaffected.