CVE-2026-23243 RDMA/umad: Reject negative data_len in ib_umad_write
A local attacker can trigger an integer overflow in the Linux kernel RDMA driver, leading to an out-of-bounds write and potential code execution or system crash.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-23243?
CVE-2026-23243 is a high-severity vulnerability in Linux kernel, published on 18 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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
Which versions are affected by CVE-2026-23243?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-23243?
Apply the vendor's patch.
Is CVE-2026-23243 being exploited?
There is no known exploitation of CVE-2026-23243 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-80004, BELL-CVE-2026-23243, DEBIAN-CVE-2026-23243, GHSA-85rq-57vx-88q2, ROOT-OS-DEBIAN-11-CVE-2026-23243, ROOT-OS-DEBIAN-12-CVE-2026-23243 and 4 more.