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CVE Record

CVE-2021-46928: parisc: Clear stale IIR value on instruction access rights trap

In the Linux kernel, the following vulnerability has been resolved: parisc: Clear stale IIR value on instruction access rights trap When a trap 7 (Instruction access rights) occurs, this means the CPU couldn't execute an instruction due to missing execute permissions on the memory region. In this case it seems the CPU didn't even fetched the instruction from memory and thus did not store it in the cr19 (IIR) register before calling the trap handler. So, the trap handler will find some random old stale value in cr19. This patch simply overwrites the stale IIR value with a constant magic "bad food" value (0xbaadf00d), in the hope people don't start to try to understand the various random IIR values in trap 7 dumps.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue affects the PA-RISC architecture’s handling of instruction access-rights traps. The documented impact is misleading stale diagnostic data in trap dumps, not a named privilege escalation or remote attack. Business urgency depends on whether you operate PA-RISC Linux systems.

Executive priority

Track and remediate during normal kernel maintenance unless PA-RISC Linux is used in critical operations. There is no sourced evidence of active exploitation or broad enterprise exposure.

Technical view

On parisc, trap 7 can occur before the CPU fetches the faulting instruction, leaving cr19/IIR with an old value. The fix overwrites that stale IIR value with 0xbaadf00d so crash diagnostics do not mislead investigators. No CVSS, CWE, or exploitation detail is provided.

Likely exposure

Exposure appears limited to Linux kernels on PA-RISC/parisc systems within the affected kernel history. Most organizations without PA-RISC Linux assets are unlikely to be exposed. Distribution backports are not described in the provided sources.

Exploitation context

The source bundle does not show active exploitation, and the CVE is not marked KEV. The available description is about stale trap-dump state, not an attacker workflow or confirmed security impact.

Researcher notes

The key behavior is stale cr19/IIR state during trap 7 when no instruction fetch occurs. The patch changes diagnostic state handling rather than documenting a conventional memory-corruption or access-control exploit primitive.

Mitigation direction

  • Identify any Linux PA-RISC/parisc systems in production or lab environments.
  • Update affected kernels to a version containing the referenced stable fixes.
  • Check Linux distribution advisories for backported fixes and package-specific status.
  • Treat this as low operational urgency unless PA-RISC systems are mission critical.

Validation and detection

  • Inventory kernel architecture and version on systems that may run PA-RISC Linux.
  • Confirm whether the parisc trap handler includes the IIR clearing change.
  • Map deployed kernels against vendor advisories or stable kernel commits.
  • Review crash-analysis procedures for possible stale IIR interpretation before patching.
Prepared
Confidence
medium
Sources
5

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-2021-46928 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
4Source 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
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2unaffected
LinuxLinux2.6.12, 0, 5.10.90, 5.15.13, 5.16affected
Weakness

CWE details

No CWE listed

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