Medium [CVE-2026-89756] Linux kernel: Denial of Service due to RCU-tasks stall during memory migration
This medium-severity Red Hat Linux advisory covers CVE-2026-89756.
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Summary
A flaw was found in the Linux kernel. When performing memory migration on KVM (Kernel-based Virtual Machine) hosts, the `migrate_pages_batch()` function fails to report RCU (Read-Copy Update) tasks quiescent states during large batch unmapping operations.
This oversight causes the migrating task to become an RCU holdout, leading to a prolonged stall in the RCU grace period. This can result in a Denial of Service (DoS) by keeping the CPU busy for an extended duration.
Red Hat severity: Moderate — CVSS 4.7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-821.
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 46 minutes 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 46 minutes ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 46 minutes ago·verify at source
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