In the Linux kernel, the following vulnerability has been resolved:

RDMA/umad: Reject negative data_len in ib_umad_write

ib_umad_write computes data_len from user-controlled count and the
MAD header sizes. With a mismatched user MAD header size and RMPP
header length, data_len can become negative and reach ib_create_send_mad().
This can make the padding calculation exceed the segment size and trigger
an out-of-bounds memset in alloc_send_rmpp_list().

Add an explicit check to reject negative data_len before creating the
send buffer.

KASAN splat:
[ 211.363464] BUG: KASAN: slab-out-of-bounds in ib_create_send_mad+0xa01/0x11b0
[ 211.364077] Write of size 220 at addr ffff88800c3fa1f8 by task spray_thread/102
[ 211.365867] ib_create_send_mad+0xa01/0x11b0
[ 211.365887] ib_umad_write+0x853/0x1c80

References

• https://nvd.nist.gov/vuln/detail/CVE-2026-23243
• https://git.kernel.org/stable/c/1371ef6b1ecf3676b8942f5dfb3634fb0648128e
• https://git.kernel.org/stable/c/205955f29c26330b1dc7fdeadd5bb97c38e26f56
• https://git.kernel.org/stable/c/362e45fd9069ffa1523f9f1633b606ebf72060d7
• https://git.kernel.org/stable/c/52ab82cc5cf8ada5c3fb6ffe8f32fdb2fc27a34b
• https://git.kernel.org/stable/c/5551b02fdbfd85a325bb857f3a8f9c9f33397ed2
• https://git.kernel.org/stable/c/6eb2919474ca105c5b13d19574e25f0ddcf19ca2
• https://git.kernel.org/stable/c/9c80d688f402539dfc8f336de1380d6b4ee14316
• https://git.kernel.org/stable/c/a6a3e4af10993cb9e4b8f0548680aba0ab5f3b0d