Security readout for executives and security teams
Plain-English summary
A failed SMB multichannel binding request can leave Linux ksmbd in the wrong internal state. Later session searches may use the global session table instead of the connection-specific path. The supplied CVSS score is 8.8, indicating potentially serious confidentiality, integrity, and availability consequences, although the source does not detail practical impact scenarios.
Executive priority
Treat this as a high-priority kernel remediation for systems actively serving SMB through ksmbd, especially externally reachable or shared file servers. First establish whether ksmbd is present and exposed, then apply supported updates. Systems not using ksmbd are unlikely to be directly exposed based on the supplied description.
Technical view
On the error path for an SMB2_SESSION_SETUP request carrying SMB2_SESSION_REQ_FLAG_BINDING, ksmbd sets conn->binding to true but fails to reset it. Subsequent ksmbd_session_lookup_all() calls then fall back to the global sessions table. The referenced Linux stable commits correct the error path by setting conn->binding to false.
Likely exposure
Exposure is limited to Linux systems running ksmbd and accepting the relevant SMB multichannel binding request. Network reachability and low privileges are reflected in the supplied CVSS vector. The bundled version data identifies affected releases from 5.15 through 7.0 entries, but its exact boundaries are ambiguous; confirm against distribution advisories and fixed commits.
Exploitation context
The supplied record does not identify active exploitation, and the CVE is not listed as KEV in the bundle. No public exploit evidence is provided. Exploitation requires network access and low privileges according to the CVSS vector, but the sources do not explain the complete path from the stale binding state to confidentiality, integrity, or availability impact.
Researcher notes
The documented defect is a persistent per-connection state error following failed multichannel binding. Its observable consequence is global-session-table fallback during later lookups. The sources provide fixes but no proof-of-concept, exploitation telemetry, CWE assignment, or detailed impact chain. Avoid assuming session takeover or code execution without further evidence.
Mitigation direction
- Apply a vendor-supported kernel update containing the applicable referenced stable fix.
- Prioritize internet-accessible or broadly reachable ksmbd servers.
- Restrict SMB access to trusted networks and authorized clients until patched.
- Disable ksmbd where it is unnecessary, following distribution guidance.
- Check Linux distribution advisories for exact affected and fixed package versions.
Validation and detection
- Confirm whether ksmbd is built, loaded, and actively serving SMB.
- Inventory kernel and distribution package versions on ksmbd hosts.
- Map deployed kernels to vendor advisories and the referenced stable commits.
- Verify the installed kernel contains the applicable binding-state fix.
- Retest SMB service availability and authentication behavior after updating.
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-2026-31409 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:L/UI:N/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:L/UI:N/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:L/UI:N/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/7e8b270813079c785696bce8802a3f920665c88cCVE reference, Linux
- https://git.kernel.org/stable/c/d073870dab8f6dadced81d13d273ff0b21cb7f4eCVE reference, Linux
- https://git.kernel.org/stable/c/6ebef4a220a1ebe345de899ebb9ae394206fe921CVE reference, Linux
- https://git.kernel.org/stable/c/89afe5e2dbea6e9d8e5f11324149d06fa3a4efcaCVE reference, Linux
- https://git.kernel.org/stable/c/9feb2d1bf86d9e5e66b8565f37f8d3a7d281a772CVE reference, Linux
- https://git.kernel.org/stable/c/6260fc85ed1298a71d24a75d01f8b2e56d489a60CVE reference, Linux
- https://git.kernel.org/stable/c/282343cf8a4a5a3603b1cb0e17a7083e4a593b03CVE 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.