CVE-2026-43258 alpha: fix user-space corruption during memory compaction
Insufficient TLB shootdown during memory compaction on Alpha systems causes user-space memory corruption, leading to crashes or potential code execution.
- 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-2026-43258?
CVE-2026-43258 is a high-severity memory corruption vulnerability in Linux kernel, published on 6 May 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:
alpha: fix user-space corruption during memory compaction
Alpha systems can suffer sporadic user-space crashes and heap corruption when memory compaction is enabled.
Symptoms include SIGSEGV, glibc allocator failures (e.g. "unaligned tcache chunk"), and compiler internal errors. The failures disappear when compaction is disabled or when using global TLB invalidation.
The root cause is insufficient TLB shootdown during page migration. Alpha relies on ASN-based MM context rollover for instruction cache coherency, but this alone is not sufficient to prevent stale data or instruction translations from surviving migration.
Fix this by introducing a migration-specific helper that combines: - MM context invalidation (ASN rollover), - immediate per-CPU TLB invalidation (TBI), - synchronous cross-CPU shootdown when required.
The helper is used only by migration/compaction paths to avoid changing global TLB semantics.
Additionally, update flush_tlb_other(), pte_clear(), to use READ_ONCE()/WRITE_ONCE() for correct SMP memory ordering.
This fixes observed crashes on both UP and SMP Alpha systems.
Weakness: CWE-787
Which versions are affected by CVE-2026-43258?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43258?
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-2026-43258 being exploited?
There is no known exploitation of CVE-2026-43258 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-85863, BELL-CVE-2026-43258, DEBIAN-CVE-2026-43258, GHSA-rj9j-qfgp-687w, ROOT-OS-DEBIAN-11-CVE-2026-43258, ROOT-OS-DEBIAN-12-CVE-2026-43258 and 3 more.