CVE-2026-52916

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.

References

• https://git.kernel.org/stable/c/0c208fa3859e3a33a1c38bebc41d021166e94ac8
• 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/aea54d0bbe156d5ab7d00d68f66149ff41f4612a