CVE-2026-31663: xfrm: hold dev ref until after transport_finish NF_HOOK

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-24 · updated 2026-10-30
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: xfrm: hold dev ref until after transport_finish NF_HOOK After async crypto completes, xfrm_input_resume() calls dev_put() immediately on re-entry before the skb reaches transport_finish. The skb->dev pointer is then used inside NF_HOOK and its okfn, which can race with device teardown. Remove the dev_put from the async resumption entry and instead drop the reference after the NF_HOOK call in transport_finish, using a saved device pointer since NF_HOOK may consume the skb. This covers NF_DROP, NF_QUEUE and NF_STOLEN paths that skip the okfn. For non-transport exits (decaps, gro, drop) and secondary async return points, release the reference inline when async is set.

Affected products

Linux kernel: from 3.2.100 before 3.3; from 3.16.55 before 3.17; from 4.14.24 before 4.15; from 4.15.1 before 6.18.23; from 6.19 before 6.19.13; 7.0-rc1, 7.0-rc2, 7.0-rc3, 7.0-rc4, 7.0-rc5, 7.0-rc6 (+1) — fixed in 3.3, 3.17, 4.15, 6.18.23, 6.19.13
Linux: from 3.2.100 before 3.3; from 3.16.55 before 3.17; from 4.14.24 before 4.15 — fixed in 3.3, 3.17, 4.15

How to fix

Upgrade to a fixed version: Linux kernel 3.3, 3.17, 4.15, 6.18.23; Linux 3.3, 3.17, 4.15. Check the vendor advisory for mitigations.

References

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