Security readout for executives and security teams
Plain-English summary
A race in Linux’s SMB client allows two background tasks to update network-interface state simultaneously. The official fix serializes that update with a lock. The CVSS score is 8.8, but the supplied evidence does not show observed attacks or explain exactly how the race produces confidentiality, integrity, and availability loss.
Executive priority
Treat this as an expedited Linux patching issue for systems using SMB clients, especially business-critical SMB workflows. The high CVSS score warrants prompt assessment, but current evidence does not justify declaring an active incident. Obtain distribution-specific package guidance before setting deadlines because the supplied version mapping is incomplete.
Technical view
In SMB client ->query_interfaces(), two work items could concurrently update interfaces. The fix checks and updates iface_last_update while holding iface_lock, preventing competing updates. CVSS 3.1 is 8.8 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H). No CWE is assigned, and the bundle does not document crash, corruption, or takeover mechanics.
Likely exposure
Linux systems running affected kernels and using SMB client interface-query functionality are the likely exposure. The affected-version data lists 5.19, 6.6.128, 6.12.75, 6.18.16, 6.19.6, 7.0, plus an unexplained “0”; it cannot establish precise distribution package ranges. Systems not using this SMB client path may have lower practical exposure.
Exploitation context
The bundle reports no active exploitation and marks KEV false. The CVSS vector indicates network reachability, low complexity, no privileges, and required user interaction. However, the description does not explain the triggering interaction, prerequisites, reliable impact, or public proof-of-concept, so real-world exploitability remains uncertain.
Researcher notes
The core evidence establishes a concurrency defect and locking fix, but not the failure manifestation or an exploitation chain. The affected data contains a duplicated commit identifier and unexplained version “0,” limiting exact boundary analysis. Review the five stable commits and distribution backports. Do not infer vulnerability solely from the upstream version number.
Mitigation direction
- Identify Linux systems that actively use SMB client functionality.
- Deploy a vendor-supported kernel package incorporating the applicable cited stable fix.
- Check distribution advisories and changelogs because the supplied affected-version data is ambiguous.
- Where patching is delayed, apply only vendor-documented mitigations; the bundle provides no workaround.
Validation and detection
- Inventory running kernel and distribution package versions on systems using SMB client functionality.
- Confirm vendor changelogs map the installed package to CVE-2026-43239 or a cited stable commit.
- After updating, verify the fixed kernel is running, not merely installed.
- Confirm iface_last_update is checked and updated under iface_lock in the deployed source or backport.
- Perform normal SMB interoperability tests after maintenance; successful operation alone does not prove non-exploitability.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2026-43239 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
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.
CVSS vector scores
1 official scoreWe 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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H2.85.9LinuxVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/93e8e3ee165ae4609a1222b516b573837103d2c3CVE reference, Linux
- https://git.kernel.org/stable/c/ab6564f416a6eaf1199200b6100952407b438f7dCVE reference, Linux
- https://git.kernel.org/stable/c/6287eefaf21ec805d42f941bd368018cf397a7f5CVE reference, Linux
- https://git.kernel.org/stable/c/76cc4faba0343c6db945b8dc75425b33d633e1b8CVE reference, Linux
- https://git.kernel.org/stable/c/c3c06e42e1527716c54f3ad2ced6a034b5f3a489CVE reference, Linux
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.