CVE-2026-63919: xfrm: input: hold netns during deferred transport reinjection
In the Linux kernel, the following vulnerability has been resolved:
xfrm: input: hold netns during deferred transport reinjection
Transport-mode reinjection stores a struct net pointer in skb->cb and uses it later from xfrmtransreinject(). That pointer must stay valid until the deferred callback runs.
Take a netns reference when queueing deferred reinjection work and drop it after the callback completes. Use maybegetnet() so the queueing path does not revive a namespace that is already being torn down.
This keeps the existing workqueue design and fixes the netns lifetime handling in one place for all users of xfrmtransqueuenet().
Other sources
In the Linux kernel, the following vulnerability has been resolved:
xfrm: input: hold netns during deferred transport reinjection
Transport-mode reinjection stores a struct net pointer in skb-cb and uses it later from xfrmtransreinject(). That pointer must stay valid until the deferred callback runs.
Take a netns reference when queueing deferred reinjection work and drop it after the callback completes. Use maybegetnet() so the queueing path does not revive a namespace that is already being torn down.
This keeps the existing workqueue design and fixes the netns lifetime handling in one place for all users of xfrmtransqueuenet().
— IBM
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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linux/Kernelto a version that resolves this vulnerability.Fixed in 5.10.259 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-28.28.1 - Compensating control
In the deferred transport reinjection path, use maybe_get_net() when queueing work through xfrm_trans_queue_net(), retain the netns reference until the deferred callback completes, then release it; this keeps the struct net pointer stored in skb->cb valid without reviving a namespace that is already being torn down.
Event History
Frequently Asked Questions
What conditions are needed to trigger this issue?
The affected path involves XFRM transport-mode deferred reinjection, where a network-namespace pointer is saved in an skb control buffer and later used by a deferred callback. Triggering it also depends on the referenced network namespace being torn down before that callback runs.
What is the practical impact of the bug?
The deferred reinjection callback can use a network-namespace pointer after its lifetime has ended. The provided CVSS vector rates the issue as network-reachable, low-complexity, requiring low privileges, with high confidentiality, integrity, and availability impact.
What mitigation is described if an update cannot be applied immediately?
The provided data does not identify a configuration workaround. The fix is to retain a network-namespace reference when deferred reinjection is queued and release it after the callback completes, while avoiding acquisition of references for namespaces already being torn down.