Security readout for executives and security teams
Plain-English summary
A remote, unauthenticated client can send a malformed compound SMB request to Linux ksmbd and trigger a NULL-pointer error. The expected impact is denial of service, potentially disrupting the host or file-sharing workload. The supplied CVSS score is 7.5; no confidentiality or integrity impact is identified.
Executive priority
Prioritize reachable production systems using ksmbd, especially internet-facing file servers or hosts where a kernel outage would interrupt critical operations. Remediation should be prompt but evidence does not support emergency incident declarations absent local indicators. Systems not using ksmbd are unlikely to be exposed.
Technical view
ksmbd failed to validate session and tree identifiers consistently across a compound SMB request. A leading SMB2 ECHO could bypass validation, leaving session or tree connection pointers NULL; a later operation could dereference them. The vector is network-accessible, low-complexity, unauthenticated, and requires no user interaction.
Likely exposure
Exposure is limited to systems using ksmbd where SMB is reachable by an attacker. The bundle lists Linux 5.15, 5.15.121, 6.1.36, 6.3.10, and 6.4, but its version structure is ambiguous. Confirm affected and fixed status using distribution guidance and backport records.
Exploitation context
The supplied record does not identify known active exploitation, and it is not marked as CISA KEV. The CVSS vector indicates remote, unauthenticated reachability and low attack complexity. Treat internet-exposed or broadly reachable ksmbd services as higher priority, without assuming exploitation has occurred.
Researcher notes
The failure is a missing validation issue resulting in NULL-pointer dereference and availability impact. The supplied affected-version array does not clearly distinguish introduced, affected, and fixed boundaries. Validate lineage using the four stable-kernel commits and distribution backports. No CWE or public exploitation evidence is supplied.
Mitigation direction
- Apply a vendor-supported kernel update containing the referenced ksmbd validation fix.
- Check distribution advisories because vendors may backport fixes without changing the upstream version as expected.
- Restrict SMB access to trusted networks while affected systems remain unpatched.
- Disable ksmbd where it is unnecessary, following vendor operational guidance.
Validation and detection
- Inventory hosts loading or configuring ksmbd and identify their exact kernel package builds.
- Determine whether SMB endpoints are reachable from untrusted or internet-facing networks.
- Compare installed packages with distribution advisories and documented backport status.
- After updating, confirm the running kernel is the remediated build.
- Review kernel logs and availability alerts for unexplained ksmbd-related NULL-pointer failures.
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
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ATT&CK lookup starting points
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CVE-2023-3866 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:N/S:U/C:N/I:N/A:H3.93.6LinuxVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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/eb947403518ea3d93f6d89264bb1f5416bb0c7d0CVE reference, Linux
- https://git.kernel.org/stable/c/854156d12caa9d36de1cf5f084591c7686cc8a9dCVE reference, Linux
- https://git.kernel.org/stable/c/d1066c1b3663401cd23c0d6e60cdae750ce00c0fCVE reference, Linux
- https://git.kernel.org/stable/c/5005bcb4219156f1bf7587b185080ec1da08518eCVE 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.