CVE-2026-64091 batman-adv: tt: fix TOCTOU race for reported vlans
A race condition in the batman-adv kernel module can cause a buffer overflow, potentially leading to a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64091?
CVE-2026-64091 is a critical vulnerability in Linux kernel, published on 19 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-367
Which versions are affected by CVE-2026-64091?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64091?
Apply the vendor's patch.
Is CVE-2026-64091 being exploited?
There is no known exploitation of CVE-2026-64091 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64091, DEBIAN-CVE-2026-64091, GHSA-r4m5-xwcp-9p7w, ROOT-OS-UBUNTU-2204-CVE-2026-64091, UBUNTU-CVE-2026-64091.