Security readout for executives and security teams
Plain-English summary
Microsoft 365 Copilot’s Business Chat could expose confidential information to an unauthorized remote attacker. The issue requires neither an account nor user interaction according to the supplied CVSS data. The available sources do not describe what data may be reached or provide technical attack details.
Executive priority
Treat this as a high-priority confidentiality risk. Determine Business Chat usage immediately and verify Microsoft’s remediation across applicable tenants. Escalation is warranted because exploitation requires no authentication or user action, although active exploitation is not established by the supplied evidence.
Technical view
CVE-2026-26164 is a CWE-74 command-injection weakness caused by improper neutralization of command elements. Its CVSS 3.1 score is 7.5: network-accessible, low complexity, no privileges, and no user interaction. The documented impact is high confidentiality loss without integrity or availability impact.
Likely exposure
Organizations using Microsoft 365 Copilot’s Business Chat are potentially exposed. The supplied record provides no affected version range or CPE, so precise tenant applicability cannot be determined from this bundle alone. Confirm service and remediation status through Microsoft’s advisory.
Exploitation context
The CVSS record describes remote, unauthenticated exploitation with low attack complexity and no user interaction. However, CVSS exploit maturity is unproven, the CVE is not listed as KEV in the bundle, and no supplied source confirms active exploitation.
Researcher notes
The vector is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C. CWE-74 supports an injection classification, but the bundle lacks affected versions, CPEs, root-cause detail, attack prerequisites beyond CVSS, indicators of compromise, and specific remediation mechanics.
Mitigation direction
- Review Microsoft’s CVE advisory and apply the official remediation it specifies.
- Prioritize remediation for every tenant using Microsoft 365 Copilot’s Business Chat.
- Follow Microsoft guidance for interim controls; none are detailed in the supplied sources.
- Minimize sensitive Business Chat exposure until remediation is confirmed, where operationally feasible.
Validation and detection
- Inventory tenants using Microsoft 365 Copilot’s Business Chat.
- Confirm remediation status against Microsoft’s current CVE advisory.
- Document applicability carefully because the supplied record identifies no affected versions.
- Monitor the Microsoft advisory and CVE record for revised exploitation or scope information.
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-74: 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-26164 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:L/PR:N/UI:N/S:U/C:H/I:N/A:N/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:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C3.93.6microsoftVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/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
- M365 Copilot Information Disclosure 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.
Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.