# CVE-2026-43258: alpha: fix user-space corruption during memory compaction

CVE-2026-43258 is fixed in 45 products on 1 platform, first by ALAS2023-2026-1543, released April 7, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-43258
- Priority: High
- CVSS: 7.8 (Moderate)
- EPSS: 0.0018
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 7, 2026
- Weakness: Out-of-bounds Write
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-43258

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | bpftool6.12 amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | bpftool6.12-debuginfo amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | bpftool6.18 amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | bpftool6.18-debuginfo amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel-livepatch-6.12.77-99.140 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel-livepatch-6.18.16-18.222 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.12 amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-debuginfo amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-debuginfo-common-aarch64 amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-debuginfo-common-x86_64 amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-devel amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-headers amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-libbpf amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-libbpf-debuginfo amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-libbpf-devel amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-libbpf-static amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-modules-extra amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-modules-extra-common amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-tools amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-tools-debuginfo amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.12-tools-devel amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | kernel6.18 amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-debuginfo amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-debuginfo-common-aarch64 amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-debuginfo-common-x86_64 amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-devel amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-headers amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-libbpf amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-libbpf-debuginfo amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-libbpf-devel amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-libbpf-static amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-modules-extra amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-modules-extra-common amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-tools amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-tools-debuginfo amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | kernel6.18-tools-devel amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.85-1 | [DEBIAN-CVE-2026-43258](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43258.md) | May 15, 2026 |
| Linux | linux Debian 14 | 6.19.6-1 | [DEBIAN-CVE-2026-43258](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43258.md) | May 15, 2026 |
| Linux | perf6.12 amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | perf6.12-debuginfo amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | perf6.18 amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | perf6.18-debuginfo amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | python3-perf6.12 amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | python3-perf6.12-debuginfo amzn 2023 | 1:6.12.77-99.140.amzn2023 | [ALAS2023-2026-1543](https://patchblox.com/security/data/fix/linux/alas2023-2026-1543.md) | Apr 7, 2026 |
| Linux | python3-perf6.18 amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |
| Linux | python3-perf6.18-debuginfo amzn 2023 | 1:6.18.16-18.222.amzn2023 | [ALAS2023-2026-1702](https://patchblox.com/security/data/fix/linux/alas2023-2026-1702.md) | May 11, 2026 |

---

Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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