CVE-2026-74694net/ncsi: fix heap OOB read in NCSI_CMD_SEND_CMD payload length

Official description

In the Linux kernel, the following vulnerability has been resolved: net/ncsi: fix heap OOB read in NCSI_CMD_SEND_CMD payload length ncsi_send_cmd_nl() takes the number of bytes to copy from the attacker-controlled ncsi_pkt_hdr.length field of the in-band packet header, while the source buffer is the NCSI_ATTR_DATA netlink attribute whose readable size is nla_len() - sizeof(ncsi_pkt_hdr). The two length sources are never cross-checked: only nla_len() >= sizeof(struct ncsi_pkt_hdr) is enforced. With hdr->length set larger than the attribute payload (up to 65535 against at most 2032 readable bytes), ncsi_cmd_handler_oem() copies past the end of the netlink attribute buffer with unsafe_memcpy(), leaking up to ~64KB of kernel heap memory into the transmitted NCSI command packet. The destination skb is sized by the declared payload, so the write side does not overflow - this is a pure OOB read / information leak, reachable with CAP_NET_ADMIN on systems with a registered NCSI device (e.g. OpenBMC on Aspeed BMC SoCs, where NET_NCSI=y is standard). Reject commands whose declared payload extends past the end of the data attribute. The issue was found by the autokbug dynamic kernel fuzzer at Tencent Yunding Lab.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/e60afa01d35f8b2671b27ca93309921427144cce
• https://git.kernel.org/stable/c/67c72b8ef63d9d9a610546fda30b116638f39745
• https://git.kernel.org/stable/c/4489b4a17892750131e4bef4bc1d3d703c8fb5ba
• https://git.kernel.org/stable/c/43c7d0a6917751ea898ae584d00f24f5deac46d4
• https://git.kernel.org/stable/c/b5231ad0b376b801ab8cf2962b182cc29deaedb3
• https://git.kernel.org/stable/c/02226af69362758046822840fc6a497f5de33f00
• https://git.kernel.org/stable/c/3a60b5af75abe8e3494ccd074fb4ae6e601a3e55
• https://git.kernel.org/stable/c/afa58b7384913c8773d837acdb07b035690ec5d2