CVE-2026-64091: batman-adv: tt: fix TOCTOU race for reported vlans
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 meshifvlanlistlock 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 Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-64091?
CVE-2026-64091 has a severity rating of critical with a CVSS score of 9.8.
How do I fix CVE-2026-64091?
To fix CVE-2026-64091, update your Linux kernel to the latest patched version where the vulnerability has been addressed.
What type of vulnerability is CVE-2026-64091?
CVE-2026-64091 is a Time-of-Check to Time-of-Use (TOCTOU) race condition vulnerability.
Which software is affected by CVE-2026-64091?
CVE-2026-64091 affects the Linux kernel, specifically the batman-adv networking module.
What are the potential impacts of CVE-2026-64091?
The potential impacts of CVE-2026-64091 include unauthorized access, data corruption, or system instability due to the TOCTOU race condition.