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CVE Record

CVE-2026-31674: netfilter: ip6t_rt: reject oversized addrnr in rt_mt6_check()

In the Linux kernel, the following vulnerability has been resolved: netfilter: ip6t_rt: reject oversized addrnr in rt_mt6_check() Reject rt match rules whose addrnr exceeds IP6T_RT_HOPS. rt_mt6() expects addrnr to stay within the bounds of rtinfo->addrs[]. Validate addrnr during rule installation so malformed rules are rejected before the match logic can use an out-of-range value.

HighCVSS 7.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux kernel netfilter flaw allows a locally authenticated, low-privileged actor to supply an oversized IPv6 route-match value. The kernel may then read beyond an internal address array, potentially exposing sensitive data or disrupting the system. Network access alone is insufficient; the attacker must be able to install the malformed rule.

Executive priority

Treat this as a high-priority local privilege-boundary issue, especially on shared hosts, appliances, and container platforms exposing firewall-rule administration. Patch during the next expedited maintenance window. Accelerate further where untrusted or semi-trusted workloads can modify netfilter configuration. Current evidence does not justify emergency incident response based on active exploitation.

Technical view

The ip6t_rt match accepted addrnr values exceeding IP6T_RT_HOPS. rt_mt6() subsequently used that value with rtinfo->addrs[], creating an out-of-bounds access. The stable-kernel correction validates addrnr during rule installation and rejects malformed rules before match processing. CVSS 3.1 is 7.1, reflecting local, low-complexity exploitation with confidentiality and availability impact.

Likely exposure

Exposure is concentrated on affected Linux systems where a less-trusted local account or workload can install IPv6 netfilter route-match rules. The supplied version data identifies multiple affected kernel lines through 7.0, but its range semantics are incomplete. Distribution-maintained kernels may carry backported fixes without changing to an obvious upstream version.

Exploitation context

The supplied evidence describes local exploitation requiring low privileges and no user interaction. It does not establish remote exploitation, public exploit availability, or observed attacks. The record is not flagged as KEV, so active exploitation should not be claimed. Exact consequences beyond the scored confidentiality and availability impacts are not documented in the bundle.

Researcher notes

The core condition is missing bounds validation for addrnr against IP6T_RT_HOPS before rt_mt6() indexes rtinfo->addrs[]. The cited kernel commits appear to be stable-branch corrections. The bundle does not provide a CWE, proof of exploitation, detailed crash behavior, or reliable distribution-package mapping. Validate exposure using vendor backport records rather than upstream version strings alone.

Mitigation direction

  • Apply a vendor-supported kernel update containing the relevant stable fix.
  • Prioritize systems allowing less-trusted users or workloads to install netfilter rules.
  • Restrict unnecessary authority to create or modify IPv6 netfilter rules.
  • Review applicable Linux distribution and Siemens advisories for product-specific remediation.
  • Follow vendor reboot or kernel-activation requirements after updating.

Validation and detection

  • Inventory running kernel versions and distribution package revisions.
  • Check vendor changelogs for CVE-2026-31674 or the referenced stable commits.
  • Identify accounts and workloads permitted to install IPv6 netfilter rules.
  • Confirm oversized addrnr rules are rejected during installation after remediation.
  • Verify the fixed kernel is active following any required restart.
Prepared
Confidence
medium
Sources
12

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-2026-31674 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.1 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/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
11Source 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
7.1CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H1.85.2Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.1High
CVSS 3.1 vector shape for CVE-2026-31674Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/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

siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2unaffected
LinuxLinux2.6.12, 0, 5.10.253, 5.15.203, 6.1.168, 6.6.131, 6.12.80, 6.18.21, 6.19.11, 7.0affected
Weakness

CWE details

No CWE listed

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