CVE-2026-64091: batman-adv: tt: fix TOCTOU race for reported vlans

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-19 · updated 2026-08-11
Weakness: CWE-367

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.

Affected products

Linux kernel: from 3.16.60 before 3.17; from 4.4.217 before 4.5; from 4.9.217 before 4.10; from 4.14.174 before 4.15; from 4.17.1 before 5.10.259; from 5.11 before 5.15.210 — fixed in 3.17, 4.10, 4.15, 4.5, 5.10.259, 5.15.210

How to fix

Upgrade to a fixed version: Linux kernel 3.17, 4.10, 4.15, 4.5. Check the vendor advisory for mitigations.

References

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