CVE-2026-31419 Linux CVE debrief

Who should care

Linux kernel maintainers, distribution security teams, and administrators running systems that use bonding mode with broadcast transmission. Systems that can experience concurrent slave enslave/release activity are the most relevant from a defensive review standpoint.

Technical summary

According to the supplied description, bond_xmit_broadcast() iterates slaves under RCU protection and clones the skb for all but the last slave, where it reuses the original skb. The old bond_is_last_slave() test was racy because concurrent slave enslave/release could change the slave list during iteration, altering which entry appeared to be last. That could make the original skb get consumed twice and trigger a use-after-free, with the provided crash showing KASAN reporting slab-use-after-free in skb_clone. The fix snapshots the slave count with READ_ONCE() before the loop and uses i + 1 == slaves_count to decide when to reuse the original skb, preserving the zero-copy optimization while making the last-slave decision stable.

Defensive priority

High. NVD classifies the issue as CVSS 7.8 (HIGH), and the flaw is a kernel memory-safety bug with confidentiality, integrity, and availability impact. The affected versions span multiple maintained Linux kernel series, so patch verification should be prioritized wherever bonding is deployed.

Recommended defensive actions

• Apply the Linux kernel patches referenced in the official stable git links.
• Upgrade affected Linux kernel installations to versions outside the NVD vulnerable ranges.
• Review deployments that use bonding broadcast transmission and confirm they are on fixed kernel builds.
• If you maintain a downstream kernel, verify the bonding broadcast transmit logic includes the stable index-based last-slave check.
• Track any vendor advisories or backports for the affected kernel branches before postponing remediation.

Evidence notes

All findings here are limited to the supplied CVE record and official links. The description explicitly attributes the bug to bond_xmit_broadcast(), notes the racy bond_is_last_slave() check, and provides a KASAN use-after-free crash in skb_clone. NVD lists the weakness as CWE-416 and assigns CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. The supplied NVD criteria mark the following ranges as vulnerable: 5.10.94-<5.11, 5.15.17-<5.16, 5.16.3-<5.17, 5.17-6.12.86, 6.13-6.18.22, 6.19-6.19.12, and 7.0 rc1 through rc6. Published at 2026-04-13T14:16:11.447Z and last modified at 2026-05-20T19:32:49.557Z.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.