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CVE Record

CVE-2026-43035: net: sched: cls_api: fix tc_chain_fill_node to initialize tcm_info to zero to prevent an info-leak

In the Linux kernel, the following vulnerability has been resolved: net: sched: cls_api: fix tc_chain_fill_node to initialize tcm_info to zero to prevent an info-leak When building netlink messages, tc_chain_fill_node() never initializes the tcm_info field of struct tcmsg. Since the allocation is not zeroed, kernel heap memory is leaked to userspace through this 4-byte field. The fix simply zeroes tcm_info alongside the other fields that are already initialized.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue can disclose 4 bytes of kernel heap memory to userspace when specific traffic-control netlink messages are built. The business impact is primarily information exposure, not confirmed code execution or service outage. Public severity and CVSS are not provided in the bundle.

Executive priority

Treat as a routine-to-prioritized kernel update item. Escalate for internet-facing appliances, multi-tenant systems, or regulated environments where kernel memory disclosure has higher sensitivity.

Technical view

tc_chain_fill_node() did not initialize the tcm_info field in struct tcmsg. Because the allocation was not zeroed, stale kernel heap data could be copied into a netlink response. The kernel fix initializes tcm_info to zero alongside other fields.

Likely exposure

Systems running affected Linux kernels and using the vulnerable traffic-control netlink path may be exposed. The bundle lists Linux as affected and includes stable kernel fixes, but it does not define distribution package status, required privileges, or affected Siemens product details.

Exploitation context

The bundle does not report active exploitation, and KEV is false. Evidence supports an information leak to userspace through a 4-byte field. It does not support claims of remote exploitation, privilege escalation, or public weaponization.

Researcher notes

The core evidence is a small uninitialized-field leak in net/sched cls_api. Missing data includes CVSS, CWE mapping, privilege requirements, distribution timelines, and proof of exploitation. Avoid broader impact claims unless a vendor advisory supplies them.

Mitigation direction

  • Apply vendor kernel updates that include the referenced stable fixes.
  • Check Linux distribution advisories for package-specific fixed versions.
  • Review the referenced Siemens advisories if Siemens products are in scope.
  • If no vendor update is available, follow vendor guidance for temporary mitigations.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, and embedded systems.
  • Compare installed kernels with vendor advisories for CVE-2026-43035.
  • Confirm the kernel source or package includes the tcm_info zero-initialization fix.
  • Track Siemens advisory applicability without assuming unnamed products are affected.
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.

ATT&CK lookup starting points

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CVE-2026-43035 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
1ADP providers
11Source links

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
LinuxLinux32a4f5ecd7381f30ae3bb36dea77a150ba68af2e, 32a4f5ecd7381f30ae3bb36dea77a150ba68af2e, 32a4f5ecd7381f30ae3bb36dea77a150ba68af2e, 32a4f5ecd7381f30ae3bb36dea77a150ba68af2e, 32a4f5ecd7381f30ae3bb36dea77a150ba68af2e, 32a4f5ecd7381f30ae3bb36dea77a150ba68af2e, 32a4f5ecd7381f30ae3bb36dea77a150ba68af2e, 32a4f5ecd7381f30ae3bb36dea77a150ba68af2eunaffected
LinuxLinux4.19, 0, 5.10.253, 5.15.203, 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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