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CVE Record

CVE-2025-21863: io_uring: prevent opcode speculation

In the Linux kernel, the following vulnerability has been resolved: io_uring: prevent opcode speculation sqe->opcode is used for different tables, make sure we santitise it against speculations.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2025-21863 is a Linux kernel flaw in io_uring, a high-performance I/O feature. The issue concerns unsafe speculative use of an opcode value. Because the CVSS vector is local, low-privilege, and high impact, exposure matters most on shared Linux systems, developer hosts, and container platforms.

Executive priority

Prioritize remediation in the next normal emergency patch cycle for shared or multi-tenant Linux environments. Single-user systems are still relevant, but business urgency is highest where untrusted local code can run.

Technical view

The resolved kernel change sanitizes sqe->opcode before it is used to index different io_uring tables, preventing opcode speculation. The supplied CVSS v3.1 score is 7.8 with local attack vector, low attack complexity, low privileges, no user interaction, and high confidentiality, integrity, and availability impact.

Likely exposure

Linux systems with affected kernel builds that expose io_uring to local users or workloads are the primary concern. The source bundle names Linux kernel versions and stable commit references, but distro backports may change version-based assessment.

Exploitation context

The source bundle does not show CISA KEV listing or cite active exploitation. Treat this as a serious local privilege or kernel-impact risk, but do not describe it as exploited in the wild from the provided evidence.

Researcher notes

The evidence identifies the vulnerable area and fix intent, but not a public exploit, CWE, or distro-specific fixed packages. Version assessment should use vendor advisories because kernel distributions often backport fixes without changing upstream version numbers.

Mitigation direction

  • Apply vendor or distribution kernel updates containing the referenced stable fixes.
  • Prioritize shared hosts, container platforms, CI runners, and multi-user Linux systems.
  • Check Linux distributor advisories for exact fixed package versions.
  • Do not rely on workarounds unless vendor guidance documents them.

Validation and detection

  • Inventory Linux kernel versions across servers, desktops, and container hosts.
  • Compare running kernels with distributor advisories and referenced stable commits.
  • Confirm patched kernels are booted, not just installed.
  • Review local-user and untrusted-workload exposure on affected systems.
Prepared
Confidence
medium
Sources
9

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

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

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CVE-2025-21863 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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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
1ADP providers
8Source links

SSVC decision data

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

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:H1.85.9CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-21863Attack 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.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxd3656344fea0339fb0365c8df4d2beba4e0089cd, d3656344fea0339fb0365c8df4d2beba4e0089cd, d3656344fea0339fb0365c8df4d2beba4e0089cd, d3656344fea0339fb0365c8df4d2beba4e0089cd, d3656344fea0339fb0365c8df4d2beba4e0089cd, d3656344fea0339fb0365c8df4d2beba4e0089cd, d3656344fea0339fb0365c8df4d2beba4e0089cdunaffected
LinuxLinux5.6, 0, 5.10.259, 5.15.209, 6.1.175, 6.6.80, 6.12.17, 6.13.5, 6.14affected
Weakness

CWE details

No CWE listed

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