Security readout for executives and security teams
Plain-English summary
A logged-in, low-privileged attacker could exploit a timing flaw in Windows SMB Server across a network to gain higher privileges. Successful exploitation could compromise confidentiality, integrity, and availability. Exploitation is considered difficult because it requires winning a race condition, but exposed or broadly accessible SMB services increase business risk.
Executive priority
Treat this as a high-priority patching and exposure-reduction issue, especially for file servers, domain-connected servers, and systems with broadly reachable SMB. It is not supported as an emergency active-exploitation event, but credentialed network attackers could obtain extensive control if successful. Track remediation through normal high-severity timelines with accelerated handling for externally exposed or critical servers.
Technical view
CVE-2026-20926 is a CWE-362 race condition caused by improper synchronization of a shared resource in Windows SMB Server. It is remotely reachable, requires low privileges, high attack complexity, and no user interaction. The CVSS 3.1 score is 7.5, with high potential impact to confidentiality, integrity, and availability.
Likely exposure
Exposure includes listed Windows 10, Windows 11, and Windows Server releases where SMB Server is present and reachable by an authorized attacker. Internet exposure, broad internal SMB access, compromised credentials, and flat networks increase concern. The bundle does not establish whether every installation enables or exposes the vulnerable service.
Exploitation context
The source bundle does not report known active exploitation, and the CVE is not identified as CISA KEV. An attacker must already have low-level authorization and network access to SMB Server. High attack complexity indicates exploitation depends on timing or concurrency conditions, reducing reliability but not eliminating risk.
Researcher notes
The supplied vector is CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H. The bundle attributes the flaw to CWE-362 but provides no vulnerable code path, race window, proof of concept, detection signature, or update identifiers. Avoid inferring exploit reliability or affected configurations beyond Microsoft’s listed products and advisory.
Mitigation direction
- Review Microsoft guidance for the applicable security update and deployment requirements.
- Prioritize supported, SMB-serving systems reachable from untrusted or broadly accessible networks.
- Restrict SMB access to required hosts, users, and network segments.
- Reduce unnecessary SMB exposure while updates are tested and deployed.
- Monitor Microsoft guidance for revised affected-version or remediation information.
Validation and detection
- Inventory systems running the listed Windows client and server releases.
- Identify which inventoried systems provide SMB Server services and who can reach them.
- Verify applicable Microsoft security updates are installed using approved management records.
- Confirm SMB access controls permit only required hosts, users, and segments.
- Review authentication and privilege events for unexpected elevation involving SMB-accessible systems.
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.
CWE-362: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupPrivilege behavior lookup
The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-20926 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
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
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.
SSVC decision data
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:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C1.65.9microsoftVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
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.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- Windows SMB Server Elevation of Privilege VulnerabilityCVE reference, microsoft · vendor-advisory, patch
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.
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.