---
id: CVE-2026-80839
title: 'batman-adv: reject unrepresentable multicast TVLV offsets'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  batman-adv: reject unrepresentable multicast TVLV offsets

  The network and transport header fields in struct sk_buff are 16-bit
  offsets from skb->head, and U16_MAX is r…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 07afe1ba288c04280622fa002ed385f1ac0b6fe6 <
    da1f5aa7ec93f2cc17f5cd30efc54f62af433cf2
  - >-
    Linux >= 07afe1ba288c04280622fa002ed385f1ac0b6fe6 <
    916ec741e65af072b98e475feaad98c063da1b7c
  - >-
    Linux >= 07afe1ba288c04280622fa002ed385f1ac0b6fe6 <
    1b466746fe109127fd983100a228cdd1f1f6ece2
  - >-
    Linux >= 07afe1ba288c04280622fa002ed385f1ac0b6fe6 <
    2b46baa591d0a7c16b62f150917187e70d053be6
  - >-
    Linux >= 07afe1ba288c04280622fa002ed385f1ac0b6fe6 <
    f12c2de4f542e3220e17e0606f492110064f04cb
  - Linux 6.8
published: '2026-09-04'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:44:32.478Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-80839'
references:
  - url: 'https://git.kernel.org/stable/c/da1f5aa7ec93f2cc17f5cd30efc54f62af433cf2'
  - url: 'https://git.kernel.org/stable/c/916ec741e65af072b98e475feaad98c063da1b7c'
  - url: 'https://git.kernel.org/stable/c/1b466746fe109127fd983100a228cdd1f1f6ece2'
  - url: 'https://git.kernel.org/stable/c/2b46baa591d0a7c16b62f150917187e70d053be6'
  - url: 'https://git.kernel.org/stable/c/f12c2de4f542e3220e17e0606f492110064f04cb'
tags:
  - cve.org
epss: 0.00168
epssPercentile: 0.05686
ingestedAt: '2026-10-19T09:16:01.501Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

batman-adv: reject unrepresentable multicast TVLV offsets

The network and transport header fields in struct sk_buff are 16-bit
offsets from skb->head, and U16_MAX is reserved as the unset transport
header value. batadv_tvlv_call_handler() sets both fields from a received
multicast TVLV without checking whether the TVLV end is representable.

If the end offset exceeds the field's range, skb_set_transport_header()
truncates it so that the transport header precedes the network header.
The negative difference is then returned by skb_network_header_len() as
a large u32. batadv_mcast_forw_packet() consequently accepts an oversized
multicast tracker and accesses memory beyond the skb data.

Add skb_set_transport_header_careful(), an offset-aware counterpart to
skb_reset_transport_header_careful(), which validates the final
head-relative offset before assigning it. Use the new helper in
batadv_tvlv_call_handler() and reject unrepresentable TVLVs before
setting the network header.

## Affected

- `Linux >= 07afe1ba288c04280622fa002ed385f1ac0b6fe6 < da1f5aa7ec93f2cc17f5cd30efc54f62af433cf2`
- `Linux >= 07afe1ba288c04280622fa002ed385f1ac0b6fe6 < 916ec741e65af072b98e475feaad98c063da1b7c`
- `Linux >= 07afe1ba288c04280622fa002ed385f1ac0b6fe6 < 1b466746fe109127fd983100a228cdd1f1f6ece2`
- `Linux >= 07afe1ba288c04280622fa002ed385f1ac0b6fe6 < 2b46baa591d0a7c16b62f150917187e70d053be6`
- `Linux >= 07afe1ba288c04280622fa002ed385f1ac0b6fe6 < f12c2de4f542e3220e17e0606f492110064f04cb`
- `Linux 6.8`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.