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CVE Record

CVE-2026-43341: net/ipv6: ioam6: prevent schema length wraparound in trace fill

In the Linux kernel, the following vulnerability has been resolved: net/ipv6: ioam6: prevent schema length wraparound in trace fill ioam6_fill_trace_data() stores the schema contribution to the trace length in a u8. With bit 22 enabled and the largest schema payload, sclen becomes 1 + 1020 / 4, wraps from 256 to 0, and bypasses the remaining-space check. __ioam6_fill_trace_data() then positions the write cursor without reserving the schema area but still copies the 4-byte schema header and the full schema payload, overrunning the trace buffer. Keep sclen in an unsigned int so the remaining-space check and the write cursor calculation both see the full schema length.

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A Linux IPv6 IOAM tracing flaw can cause the kernel to write beyond a trace buffer because a maximum-length value wraps to zero. This memory corruption is rated critical and could threaten confidentiality, integrity, and availability. Actual exploitability depends on whether the affected IOAM6 processing path is enabled and reachable.

Executive priority

Treat this as an urgent patch-validation issue for exposed network infrastructure. Rapidly identify affected kernels and IOAM6 reachability, then apply supported updates. Systems without demonstrated IOAM6 exposure still need timely build verification because the potential consequence is kernel memory corruption, although real-world exploitation has not been established.

Technical view

In ioam6_fill_trace_data(), the schema contribution was stored in a u8. With bit 22 and a 1,020-byte schema payload, 256 wraps to zero, bypassing the remaining-space check. The subsequent function still copies the schema header and payload beyond the trace buffer. The stable fix retains sclen as an unsigned int.

Likely exposure

The supplied affected data names Linux 5.15 and specific releases through 7.0. Highest concern applies to systems where IPv6 IOAM6 trace processing is present and reachable, particularly network-facing infrastructure. Distribution-specific backports and exact vulnerable build boundaries are not established by the bundle, so kernel version strings alone may be insufficient.

Exploitation context

The supplied CVSS vector describes an unauthenticated, low-complexity network attack requiring no user interaction. However, the bundle marks this CVE as absent from KEV and provides no evidence of active exploitation, public exploit availability, or demonstrated code execution. Practical triggering prerequisites are incompletely documented.

Researcher notes

Do not equate the network CVSS vector with universal reachability. The sources establish the integer wraparound and buffer overrun, but not required configuration, packet-path constraints, crash signatures, exploit reliability, privilege outcomes, or distribution backports. Exact exposure should be determined per running build and deployment configuration.

Mitigation direction

  • Apply the vendor kernel update containing the relevant stable fix for each deployed branch.
  • Check Linux distribution advisories for affected build ranges and supported backports.
  • Prioritize systems where IPv6 IOAM6 trace processing may be externally reachable.
  • If patching is delayed, request vendor-supported mitigations; none are specified in the supplied sources.
  • Ensure the updated kernel becomes active using the platform's supported activation procedure.

Validation and detection

  • Inventory active kernel builds across hosts, appliances, containers, and network infrastructure.
  • Compare exact distribution builds with vendor advisories and the referenced stable fixes.
  • Determine whether IPv6 IOAM6 trace processing is enabled and reachable in each deployment.
  • Confirm source or backport changes sclen from u8 to unsigned int.
  • After remediation, verify the fixed kernel is active and repeat vulnerability scanning.
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

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CVE-2026-43341 mapping review

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/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
8Source 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
9.8CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

9.8Critical
CVSS 3.1 vector shape for CVE-2026-43341Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/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
LinuxLinux8c6f6fa6772696be0c047a711858084b38763728, 8c6f6fa6772696be0c047a711858084b38763728, 8c6f6fa6772696be0c047a711858084b38763728, 8c6f6fa6772696be0c047a711858084b38763728, 8c6f6fa6772696be0c047a711858084b38763728, 8c6f6fa6772696be0c047a711858084b38763728, 8c6f6fa6772696be0c047a711858084b38763728unaffected
LinuxLinux5.15, 0, 5.15.210, 6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12, 7.0affected
Weakness

CWE details

No CWE listed

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