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CVE Record

CVE-2025-40139: smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().

In the Linux kernel, the following vulnerability has been resolved: smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set(). smc_clc_prfx_set() is called during connect() and not under RCU nor RTNL. Using sk_dst_get(sk)->dev could trigger UAF. Let's use __sk_dst_get() and dev_dst_rcu() under rcu_read_lock() after kernel_getsockname(). Note that the returned value of smc_clc_prfx_set() is not used in the caller. While at it, we change the 1st arg of smc_clc_prfx_set[46]_rcu() not to touch dst there.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux kernel networking flaw can cause memory to be accessed after it has been freed during an SMC connection. A local, low-privileged attacker may be able to trigger serious confidentiality, integrity, or availability impacts. The supplied CVSS score is 7.8, but the sources do not establish active exploitation.

Executive priority

Schedule prompt remediation, prioritizing systems with untrusted local users or shared workloads. Treat this as high priority rather than an emergency internet-wide incident because exploitation requires local access and the supplied sources provide no evidence of active exploitation.

Technical view

During connect(), smc_clc_prfx_set() accessed sk_dst_get(sk)->dev without RCU or RTNL protection, creating a potential use-after-free. The correction accesses the destination and device through RCU-safe helpers under rcu_read_lock() after kernel_getsockname().

Likely exposure

Exposure requires a Linux kernel build containing the vulnerable SMC implementation and a reachable SMC connection path. The supplied affected-version data is ambiguous, so organizations should map deployed kernel packages against vendor advisories and the referenced stable commits rather than relying solely on the listed version strings.

Exploitation context

The CVSS vector describes local access, low privileges, low complexity, and no user interaction, with potentially high confidentiality, integrity, and availability impact. The CVE is not listed as KEV in the supplied bundle, and no cited source confirms public or active exploitation.

Researcher notes

The vulnerable access occurs during connect() without RCU or RTNL protection. The fix uses __sk_dst_get() and dst_dev_rcu() under an RCU read lock and adjusts helper arguments to avoid touching dst there. The caller does not use smc_clc_prfx_set()'s returned value.

Mitigation direction

  • Update to a vendor-supported kernel release containing the referenced stable correction.
  • Check distribution or appliance-vendor guidance for package-specific fixed versions.
  • Prioritize multi-user systems where untrusted local users can reach SMC functionality.
  • Apply vendor-provided compensating controls if an immediate kernel update is unavailable.

Validation and detection

  • Inventory running kernel versions across Linux hosts and appliances.
  • Compare each kernel package with vendor guidance and the referenced stable commits.
  • Confirm the corrected kernel is active after maintenance.
  • Assess whether affected systems expose or use the SMC connection path.
  • Review kernel telemetry for relevant crashes, while recognizing absence does not prove safety.
Prepared
Confidence
medium
Sources
4

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-2025-40139 mapping review

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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
0ADP providers
3Source 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
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-40139Attack 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.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxa046d57da19f812216f393e7c535f5858f793ac3, a046d57da19f812216f393e7c535f5858f793ac3unaffected
LinuxLinux4.11, 0, 6.17.3, 6.18affected
Weakness

CWE details

No CWE listed

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