CVE-2026-64091
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk43th percentile - higher than 43% of all known CVEs
Summary
A TOCTOU (time-of-check time-of-use) vulnerability was found in the Linux kernel's batman-adv implementation. During local TT-based TVLV generation, the VLAN count is checked first, then a buffer is allocated. Despite holding a lock, the number of TT entries per VLAN can increase between check and allocation, causing a buffer overflow.
Risk Assessment
An attacker could exploit this flaw to cause a buffer overflow, leading to system crash (DoS) or potential privilege escalation in network virtualization environments.
Recommendation
Apply the Linux kernel patch addressing the batman-adv TOCTOU issue immediately. Update to a kernel version containing the fix commit.
Original NVD description (English source)
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.