CVE-2026-53187 RDMA/core: Validate cpu_id against nr_cpu_ids in DMAH alloc
A local attacker can trigger an out-of-bounds read or kernel panic in the Linux kernel RDMA subsystem by providing an invalid CPU ID during DMA handle allocation.
- 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-2026-53187?
CVE-2026-53187 is a high-severity memory corruption vulnerability in Linux kernel, published on 25 Jun 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/core: Validate cpu_id against nr_cpu_ids in DMAH alloc
The cpu_id attribute supplied by user space through UVERBS_ATTR_ALLOC_DMAH_CPU_ID is passed directly to cpumask_test_cpu() without first verifying that the value is within the valid CPU range.
Passing such untrusted data to cpumask_test_cpu() may lead to an out-of-bounds read of the underlying cpumask bitmap: the helper expands to a test_bit() that indexes the bitmap by cpu_id / BITS_PER_LONG with no bound check.
In addition, on kernels built with CONFIG_DEBUG_PER_CPU_MAPS it trips the WARN_ON_ONCE() in cpumask_check(); combined with panic_on_warn this turns a bad user input into a machine reboot.
Reject any cpu_id that is not smaller than nr_cpu_ids with -EINVAL before it is used.
Reported by Smatch.
Which versions are affected by CVE-2026-53187?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53187?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-53187 being exploited?
There is no known exploitation of CVE-2026-53187 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-53187, DEBIAN-CVE-2026-53187, GHSA-rc47-m48r-2657, UBUNTU-CVE-2026-53187.