CVE-2026-64091 Linux CVE debrief

Who should care

Linux kernel users and administrators should review and apply patches for CVE-2026-64091. Affected operators, platforms, and security teams should assess the vulnerability's impact and prioritize patching or mitigation efforts.

Technical summary

The Linux kernel has a vulnerability in the batman-adv module, specifically in the tt component. The vulnerability is related to a TOCTOU (Time-of-Check-to-Time-of-Use) race condition for reported VLANs. The issue arises from the way the local TT based TVLV is generated, which involves checking the number of VLANs with at least one TT entry, allocating a buffer, and then filling the VLAN entries in the buffer. During this process, the meshif_vlan_list_lock is held, but the actual number of TT entries of each VLAN can still increase.

Defensive priority

Medium

Recommended defensive actions

• Review and apply patches for CVE-2026-64091
• Monitor Linux kernel updates for CVE-2026-64091
• Perform inventory checks for Linux kernel versions and variants in use
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record was published on 2026-07-19T16:17:49.967Z and has not been modified since then. The NVD entry is currently Received. There is limited information available about the vulnerability, and defenders should verify the affected scope and severity with the official advisory.

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.