Medium [CVE-2026-53187] Validate cpu_id against nr_cpu_ids in DMAH alloc
This medium-severity Red Hat Linux advisory covers CVE-2026-53187 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat package: kernel-rt.
Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.
VulniPulse record published Record updated
Summary
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. A local attacker could supply an invalid `cpu_id` through the `UVERBS_ATTR_ALLOC_DMAH_CPU_ID` attribute without proper validation.
On systems configured with `CONFIG_DEBUG_PER_CPU_MAPS` and `panic_on_warn`, this vulnerability could result in a system reboot, leading to a denial of service. Red Hat severity: Moderate — CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-125. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 9.
Red Hat does not currently list a fixing RHSA for this CVE.
Is CVE-2026-53187 exploited?
No exploitation is reported in the sources VulniPulse tracks: CVE-2026-53187 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.
How do I fix CVE-2026-53187?
The advisory VulniPulse tracks names no fixed release. Follow Red Hat's guidance for workarounds and updates.
Confirm against the vendor advisory before you patch.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · medium-confidence parse· fetched 15 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 15 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That does not mean no fix exists. Read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 15 days ago·verify at source
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