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CVE Record

CVE-2026-43011: net/x25: Fix potential double free of skb

In the Linux kernel, the following vulnerability has been resolved: net/x25: Fix potential double free of skb When alloc_skb fails in x25_queue_rx_frame it calls kfree_skb(skb) at line 48 and returns 1 (error). This error propagates back through the call chain: x25_queue_rx_frame returns 1 | v x25_state3_machine receives the return value 1 and takes the else branch at line 278, setting queued=0 and returning 0 | v x25_process_rx_frame returns queued=0 | v x25_backlog_rcv at line 452 sees queued=0 and calls kfree_skb(skb) again This would free the same skb twice. Looking at x25_backlog_rcv: net/x25/x25_in.c:x25_backlog_rcv() { ... queued = x25_process_rx_frame(sk, skb); ... if (!queued) kfree_skb(skb); }

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 kernel error can free the same network packet memory twice when allocation fails in the X.25 receive path. This may crash the system or corrupt kernel memory. The supplied CVSS score is 9.8, but practical exposure depends on whether affected X.25 functionality is present and reachable.

Executive priority

Treat as an urgent investigation and patching item because kernel memory corruption can cause severe outages and the supplied severity is critical. Prioritize systems using X.25 and critical appliances. Avoid assuming every Linux host is remotely exploitable; confirm configuration and vendor package status first.

Technical view

In x25_queue_rx_frame, an allocation failure frees the skb and returns an error. That result propagates as queued=0 to x25_backlog_rcv, which frees the same skb again. Linux stable commits are supplied as fixes. The bundle does not establish reliable code-execution impact or provide distribution-specific package mappings.

Likely exposure

Likely exposure is limited to systems running affected Linux kernels where the kernel X.25 receive path is available and exercised. The supplied affected-version data is broad and contains ambiguous entries, so administrators should determine exposure using their Linux distributor’s package guidance and the referenced stable fixes.

Exploitation context

The supplied CVSS vector characterizes this as network-accessible, low-complexity, unauthenticated, and requiring no user interaction. However, the source bundle provides no proof of exploitation, exploit availability, or attacker-controlled code execution. It is not listed in KEV.

Researcher notes

The confirmed defect is a double free caused by inconsistent skb ownership during an allocation-failure path. The bundle identifies multiple stable-tree fixes but does not document trigger reliability, reachable protocol states, exploit primitives, or distribution backports. Version entries include duplicates and ambiguous values, limiting precise exposure conclusions.

Mitigation direction

  • Upgrade to a vendor-supported kernel containing the applicable referenced Linux stable fix.
  • Check Linux distributor guidance for corrected package versions and required reboot instructions.
  • Review the supplied Siemens advisories if affected systems include relevant Siemens products.
  • Prioritize externally reachable or operationally critical systems using X.25 networking.

Validation and detection

  • Inventory running kernel versions and identify systems configured for X.25 networking.
  • Map installed distribution packages to vendor-fixed versions or the applicable stable commit.
  • After updating and rebooting, verify the running kernel is the corrected build.
  • Review kernel logs for memory-corruption, double-free, or unexplained crash indicators.
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-2026-43011 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
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
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-2026-43011Attack 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.

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, 6.6.134, 6.12.81, 6.18.22, 6.19.12, 7.0affected
Weakness

CWE details

No CWE listed

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