CVE-2026-52934: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-52934 Overview

CVE-2026-52934 is an integer overflow vulnerability in the Linux kernel's batman-adv mesh networking module. The flaw resides in batadv_tvlv_container_list_size(), which used a u16 accumulator to sum the sizes of all registered TVLV (Type-Length-Value) containers. When the accumulated size exceeds U16_MAX, the value wraps, causing batadv_tvlv_container_ogm_append() to allocate an undersized buffer. The subsequent memcpy-style copy writes past the end of the allocation, corrupting kernel memory. Upstream maintainers resolved the issue by widening the return type to size_t and checking against U16_MAX before allocation.

Critical Impact
An integer wraparound triggers a kernel heap buffer overflow in batman-adv, enabling kernel memory corruption that can lead to denial of service or privilege escalation on affected systems.

Affected Products

Linux kernel versions containing the batman-adv module prior to the upstream fixes
Distributions shipping vulnerable stable kernel branches referenced in the patch commits
Mesh networking deployments relying on B.A.T.M.A.N. Advanced routing

Discovery Timeline

2026-06-24 - CVE-2026-52934 published to NVD
2026-06-24 - Last updated in NVD database

Technical Details for CVE-2026-52934

Vulnerability Analysis

The batman-adv module implements the B.A.T.M.A.N. Advanced layer 2 mesh routing protocol. It uses TVLV containers to attach extensible metadata to outgoing Originator Messages (OGMs). The function batadv_tvlv_container_ogm_append() builds a TVLV packet section by iterating over tvlv.container_list and copying each entry into a freshly allocated buffer.

The size of that buffer is determined by batadv_tvlv_container_list_size(), which previously returned a u16 and accumulated container lengths into a u16 variable. If the combined size of registered containers exceeds 65,535 bytes, the accumulator wraps to a small value. The caller then allocates a buffer based on this truncated length while the copy loop continues to write the full, untruncated payload, producing an out-of-bounds write into adjacent kernel heap memory.

Root Cause

The root cause is a numeric truncation error in size accounting. Using a 16-bit type to sum quantities that can collectively exceed 16 bits allowed silent wraparound. The fix widens the return type to size_t and adds an explicit U16_MAX bound check in batadv_tvlv_container_ogm_append(), treating the over-limit case as an allocation failure.

Attack Vector

Exploitation requires the ability to influence the contents of the TVLV container list on a host running batman-adv. An attacker with sufficient local privilege to register TVLV containers, or in scenarios where container registration is driven by network-observed state, can force the accumulator to wrap. The resulting heap overflow corrupts kernel memory, with potential outcomes ranging from a kernel panic to controlled write primitives suitable for privilege escalation.

No verified public exploit code is available. See the upstream stable tree commits including Linux Kernel Commit 13493b00 and Linux Kernel Commit f50487e for the patch details.

Detection Methods for CVE-2026-52934

Indicators of Compromise

Unexpected kernel oops or panic messages referencing batadv_tvlv_container_ogm_append or batadv_tvlv_container_list_size in dmesg or /var/log/kern.log.
SLUB/SLAB allocator warnings, KASAN out-of-bounds write reports, or page heap corruption traces tied to the batman_adv module.
Unexplained reboots or module faults on hosts where the batman_adv kernel module is loaded.

Detection Strategies

Inventory Linux hosts running the batman_adv module via lsmod | grep batman_adv and correlate kernel versions against the patched stable releases listed in the upstream commits.
Enable KASAN on test or canary kernels to surface out-of-bounds writes originating in batman-adv code paths during fuzzing.
Monitor for abnormal volumes of TVLV container registrations or large OGM payloads on mesh interfaces.

Monitoring Recommendations

Forward kernel ring buffer messages to a centralized log platform and alert on stack traces referencing batadv_tvlv_* symbols.
Track loaded kernel modules across the fleet and flag the presence of batman_adv on systems where mesh networking is not authorized.
Audit privileged userland tools (such as batctl) that interact with batman-adv for unexpected invocations.

How to Mitigate CVE-2026-52934

Immediate Actions Required

Apply vendor kernel updates that incorporate the batman-adv TVLV size widening patches to all affected hosts.
On systems that do not require mesh networking, unload and blacklist the batman_adv module to remove the attack surface entirely.
Restrict local access and capabilities (notably CAP_NET_ADMIN) on hosts that must continue running batman-adv.

Patch Information

The vulnerability is fixed across multiple Linux stable branches. Relevant upstream commits include Linux Kernel Commit 13493b00, Linux Kernel Commit 1595628a, Linux Kernel Commit 6448a49, Linux Kernel Commit 94a3d72, Linux Kernel Commit 94db72e, Linux Kernel Commit c02aa6c, Linux Kernel Commit ede4798, and Linux Kernel Commit f50487e. Update to a kernel release that includes the patch for your distribution.

Workarounds

Blacklist the module by adding blacklist batman_adv to /etc/modprobe.d/batman-adv-blacklist.conf and rebuilding the initramfs.
If batman-adv must remain loaded, limit TVLV container registration to trusted processes and reduce exposure of mesh interfaces to untrusted networks.
Enable kernel hardening features such as KASLR, SLAB hardening, and CONFIG_FORTIFY_SOURCE to raise the cost of exploiting heap corruption.

bash

# Configuration example: blacklist the batman_adv module
echo 'blacklist batman_adv' | sudo tee /etc/modprobe.d/batman-adv-blacklist.conf
sudo modprobe -r batman_adv
sudo update-initramfs -u