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CVE Record

CVE-2021-47463: mm/secretmem: fix NULL page->mapping dereference in page_is_secretmem()

In the Linux kernel, the following vulnerability has been resolved: mm/secretmem: fix NULL page->mapping dereference in page_is_secretmem() Check for a NULL page->mapping before dereferencing the mapping in page_is_secretmem(), as the page's mapping can be nullified while gup() is running, e.g. by reclaim or truncation. BUG: kernel NULL pointer dereference, address: 0000000000000068 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 6 PID: 4173897 Comm: CPU 3/KVM Tainted: G W RIP: 0010:internal_get_user_pages_fast+0x621/0x9d0 Code: <48> 81 7a 68 80 08 04 bc 0f 85 21 ff ff 8 89 c7 be RSP: 0018:ffffaa90087679b0 EFLAGS: 00010046 RAX: ffffe3f37905b900 RBX: 00007f2dd561e000 RCX: ffffe3f37905b934 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffe3f37905b900 ... CR2: 0000000000000068 CR3: 00000004c5898003 CR4: 00000000001726e0 Call Trace: get_user_pages_fast_only+0x13/0x20 hva_to_pfn+0xa9/0x3e0 try_async_pf+0xa1/0x270 direct_page_fault+0x113/0xad0 kvm_mmu_page_fault+0x69/0x680 vmx_handle_exit+0xe1/0x5d0 kvm_arch_vcpu_ioctl_run+0xd81/0x1c70 kvm_vcpu_ioctl+0x267/0x670 __x64_sys_ioctl+0x83/0xa0 do_syscall_64+0x56/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-47463 is a Linux kernel bug that can dereference a missing memory mapping and crash in kernel code. The public record shows a fix, but no CVSS score, CWE, or active exploitation evidence. Treat it mainly as an availability and stability risk for affected Linux 5.14-era systems.

Executive priority

Schedule normal patch remediation, with higher priority for virtualization hosts or systems where kernel crashes would disrupt critical services. There is no source-backed evidence of active exploitation, but kernel availability bugs can still create operational risk.

Technical view

The flaw is in page_is_secretmem(), where page->mapping could become NULL while get_user_pages_fast() was running, for example during reclaim or truncation. The fix adds a NULL check before dereferencing the mapping. The included trace shows a kernel NULL pointer dereference during a KVM page-fault path.

Likely exposure

Exposure appears limited to Linux kernels in the affected 5.14 range before the referenced stable fixes. Systems using virtualization or memory paths that exercise get_user_pages may be more likely to encounter the crash condition, but the bundle does not establish a remote attack surface.

Exploitation context

The source bundle does not show active exploitation, a public exploit, or KEV listing. It documents a kernel crash scenario and the code-level fix. Privilege requirements and reliable attacker control are not established by the provided sources.

Researcher notes

Evidence is narrow but concrete: a NULL page->mapping race in secretmem checking was fixed by adding a guard. The call trace reaches KVM handling through get_user_pages_fast. The bundle lacks CVSS, CWE, exploitability analysis, and distribution-specific affected package data.

Mitigation direction

  • Update affected Linux kernels to a version containing the referenced stable fixes.
  • Check Linux distribution advisories for backported fixes for CVE-2021-47463.
  • Prioritize hosts running kernel 5.14-era builds and virtualization workloads.
  • Avoid direct wrangler or deployment assumptions; follow normal vendor patch guidance.

Validation and detection

  • Inventory Linux kernel versions across servers, hosts, and images.
  • Confirm whether vendor kernels include the two referenced stable commits.
  • Review kernel logs for NULL pointer dereferences involving page_is_secretmem or get_user_pages_fast.
  • Check virtualization hosts for related KVM page-fault crash traces.
Prepared
Confidence
medium
Sources
4

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-47463 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
3Timeline events
2ADP providers
3Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

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.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1507f51255c9ff07d75909a84e7c0d7f3c4b2f49, 1507f51255c9ff07d75909a84e7c0d7f3c4b2f49unaffected
LinuxLinux5.14, 0, 5.14.15, 5.15affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.