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CVE Record

CVE-2021-47066: async_xor: increase src_offs when dropping destination page

In the Linux kernel, the following vulnerability has been resolved: async_xor: increase src_offs when dropping destination page Now we support sharing one page if PAGE_SIZE is not equal stripe size. To support this, it needs to support calculating xor value with different offsets for each r5dev. One offset array is used to record those offsets. In RMW mode, parity page is used as a source page. It sets ASYNC_TX_XOR_DROP_DST before calculating xor value in ops_run_prexor5. So it needs to add src_list and src_offs at the same time. Now it only needs src_list. So the xor value which is calculated is wrong. It can cause data corruption problem. I can reproduce this problem 100% on a POWER8 machine. The steps are: mdadm -CR /dev/md0 -l5 -n3 /dev/sdb1 /dev/sdc1 /dev/sdd1 --size=3G mkfs.xfs /dev/md0 mount /dev/md0 /mnt/test mount: /mnt/test: mount(2) system call failed: Structure needs cleaning.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-47066 is a Linux kernel RAID5 parity calculation bug that can produce incorrect XOR results and lead to data corruption. The public record describes reliable reproduction on a POWER8 system, but does not show remote exploitation, privilege escalation, or active exploitation evidence.

Executive priority

Treat as a storage integrity risk, not an internet-facing emergency. Prioritize remediation where Linux RAID5 protects important data, because silent or repeated corruption can create operational and recovery impact.

Technical view

The flaw is in Linux kernel async_xor handling when ASYNC_TX_XOR_DROP_DST is used in RAID5 read-modify-write mode. src_list was advanced without matching src_offs adjustment, causing parity XOR calculation with the wrong offsets and possible filesystem corruption.

Likely exposure

Exposure is most relevant to Linux systems using md RAID5 paths affected by the listed kernel versions or commits. General Linux hosts not using the affected RAID5 parity workflow are less likely to be exposed based on the source bundle.

Exploitation context

The source bundle marks KEV as false and provides no evidence of active exploitation. The described impact is corruption during a storage operation, with a reproducible failure scenario, not a documented attacker-driven exploit path.

Researcher notes

Evidence is limited to the CVE record and kernel stable references. No CVSS, CWE, exploit activity, or broad product matrix is provided. The strongest technical signal is the kernel description tying incorrect src_offs handling to data corruption.

Mitigation direction

  • Check Linux distribution advisories for fixed kernel packages covering CVE-2021-47066.
  • Upgrade to a kernel containing the referenced stable fixes or vendor backports.
  • Prioritize systems using md RAID5 or related parity configurations.
  • Review storage health and backups before kernel maintenance on affected systems.

Validation and detection

  • Inventory Linux kernel versions on RAID5 storage hosts.
  • Confirm whether md RAID5 is in use on production or backup systems.
  • Map installed kernels against vendor advisories and referenced stable commits.
  • Check system and filesystem logs for corruption or mount errors.
  • Verify backups and restore procedures for exposed storage systems.
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

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.

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CVE-2021-47066 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
5Source 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
LinuxLinux29bcff787a2593b2126cfaff612c0b4e560022e9, 29bcff787a2593b2126cfaff612c0b4e560022e9, 29bcff787a2593b2126cfaff612c0b4e560022e9, 29bcff787a2593b2126cfaff612c0b4e560022e9unaffected
LinuxLinux5.10, 0, 5.10.37, 5.11.21, 5.12.4, 5.13affected
Weakness

CWE details

No CWE listed

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