CVE-2026-64091: Linux Kernel vulnerability (CVSS 9.8)

Description

In the Linux kernel, the following vulnerability has been resolved: batman-adv: tt: fix TOCTOU race for reported vlans The local TT based TVLV is generated by first checking the number of VLANs which have at least one TT entry. A new buffer with the correct size for the VLANs is then allocated. Only then, the list of VLANs s used to fill the VLAN entries in the buffer. During this time, the meshif_vlan_list_lock is held. But the actual number of TT entries of each VLAN can still increase during this time - just not the number of VLANs in the list. But the prefilter used in the buffer size calculation might still cause an increase of the number of VLANs which need to be stored. Simply because a VLAN might now suddenly have at least one entry when it had none in the pre-alloc check - and then needs to occupy space which was not allocated. It is better to overestimate the buffer size at the beginning and then fill the buffer only with the VLANs which are not empty.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Linux Kernel≥ 3.16.60 < 3.17 · ≥ 4.14.174 < 4.15 · ≥ 4.17.1 < 5.10.259 · ≥ 4.4.217 < 4.5

Remediation

Fixed in

Linux Kernel≥ 3.17

Patch & vendor advisories

References

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-64091 being actively exploited?

CVE-2026-64091 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.43%.

How severe is CVE-2026-64091?

CVE-2026-64091 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.43% probability of exploitation.

Which products are affected by CVE-2026-64091?

Affected products include Linux Kernel.

How do I fix CVE-2026-64091?

Upgrade affected software to a fixed version, for example Linux Kernel 3.17 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-64091 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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