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CVE Record

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

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.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux kernel flaw on Alpha systems can corrupt application memory during memory compaction, causing unpredictable crashes, allocator failures, or incorrect program behavior. The issue affects system reliability and may compromise confidentiality and integrity when triggered locally. The supplied record rates it CVSS 7.8.

Executive priority

Treat confirmed Alpha deployments as a high-priority reliability and security issue, especially where untrusted local users or critical workloads exist. Expedite vendor-supported kernel updates. Organizations without Alpha systems can document non-exposure after inventory validation rather than initiating broad emergency patching.

Technical view

During page migration, Alpha's ASN-based memory-context rollover may leave stale data or instruction translations in CPU TLBs. The kernel fix adds migration-specific context invalidation, immediate per-CPU TLB invalidation, synchronous cross-CPU shootdown when required, and stronger SMP memory-access ordering. Reported failures affect both uniprocessor and multiprocessor Alpha systems.

Likely exposure

Exposure is limited to Linux systems using the Alpha architecture where memory compaction or page migration occurs. The supplied affected-version data spans multiple kernel releases but is not sufficiently clear for precise branch-level conclusions. Non-Alpha systems are not identified as affected by these sources.

Exploitation context

The CVSS vector describes local access, low complexity, low privileges, and no user interaction. However, the supplied sources do not establish a reliable exploitation method or active exploitation, and the CVE is not listed as KEV in the bundle. Observed evidence concerns sporadic corruption and crashes.

Researcher notes

The fix is deliberately scoped to migration and compaction rather than changing global TLB semantics. The record also changes flush_tlb_other() and pte_clear() to use READ_ONCE()/WRITE_ONCE() for SMP ordering. Exact vulnerable-to-fixed version boundaries and distribution backport status require vendor confirmation.

Mitigation direction

  • Install a vendor-supported kernel containing the applicable stable fix or backport.
  • If patching is delayed, consult vendor guidance about temporarily disabling memory compaction.
  • Assess operational consequences before changing compaction or TLB behavior.
  • Prioritize affected multi-user or workload-dense Alpha systems.

Validation and detection

  • Inventory Linux hosts and confirm whether any use the Alpha architecture.
  • Record kernel versions and map them against distribution advisories and relevant stable commits.
  • Verify the installed kernel includes the applicable fix or vendor backport.
  • Review logs for unexplained SIGSEGV events, allocator corruption, and compiler internal errors.
  • Retest compaction-intensive workloads after remediation and monitor for recurrence.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2026-43258 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
0ADP providers
5Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2026-43258Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxa48d07afdf18212de22b959715b16793c5a6e57a, a48d07afdf18212de22b959715b16793c5a6e57a, a48d07afdf18212de22b959715b16793c5a6e57a, a48d07afdf18212de22b959715b16793c5a6e57aunaffected
LinuxLinux2.6.16, 0, 6.12.75, 6.18.16, 6.19.6, 7.0affected
Weakness

CWE details

No CWE listed

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