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CVE-2026-69356 Microsoft CVE debrief

Microsoft Exchange Server Spoofing Vulnerability allows unauthorized attackers to perform spoofing over a network due to improper neutralization of input during web page generation. This vulnerability has a critical CVSS score of 9.3. Defenders responsible for Microsoft Exchange Server instances should assess exposure and prioritize updates to prevent potential spoofing attacks. The vulnerability exists in Microsoft Exchange Server due to improper neutralization of input during web page generation, allowing attackers to perform spoofing over a network. Defenders should prioritize verifying and updating Microsoft Exchange Server instances to prevent potential spoofing attacks.

Vendor
Microsoft
Product
Microsoft Exchange Server 2016 Cumulative Update 23
CVSS
CRITICAL 9.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-08
Original CVE updated
2026-10-08
Advisory published
2026-09-08
Advisory updated
2026-10-08

Who should care

Defenders responsible for Microsoft Exchange Server instances should assess exposure and prioritize updates to prevent potential spoofing attacks.

Why it matters

CVE-2026-69356 is a critical vulnerability in Microsoft Exchange Server that allows unauthorized attackers to perform spoofing over a network. Defenders should prioritize verifying and updating Microsoft Exchange Server instances to prevent potential spoofing attacks.

  • Verify and update Microsoft Exchange Server instances to prevent potential spoofing attacks.
  • Implement proper input validation and sanitization for web page generation.
  • Monitor for suspicious activity and potential spoofing attempts.

Technical summary

The vulnerability exists in Microsoft Exchange Server due to improper neutralization of input during web page generation, allowing attackers to perform spoofing over a network. This vulnerability has a critical CVSS score of 9.3 and allows unauthorized attackers to perform spoofing over a network. Defenders should prioritize verifying and updating Microsoft Exchange Server instances to prevent potential spoofing attacks. The vulnerability has been identified in Microsoft Exchange Server, and defenders should implement proper input validation and sanitization for

Defensive priority

Defenders should prioritize verifying and updating Microsoft Exchange Server instances to prevent potential spoofing attacks.

Recommended defensive actions

  • Verify and update Microsoft Exchange Server instances to the latest versions.
  • Implement proper input validation and sanitization for web page generation.
  • Monitor for suspicious activity and potential spoofing attempts.

Evidence notes

The CVE record and source item provide details on the vulnerability, its impact, and affected versions of Microsoft Exchange Server. The vulnerability has a critical CVSS score of 9.3 and allows unauthorized attackers to perform spoofing over a network. Defenders should verify and update Microsoft Exchange Server instances to the latest versions and implement proper input validation and sanitization for web page generation. The source item provides details on the vulnerability, and the

Sources and references

Verified primary and authoritative sources

  • CVE-2026-69356 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-69356

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-69356 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-69356

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Microsoft Exchange Server Spoofing Vulnerability

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/69xxx/CVE-2026-69356.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69356

    Supplemental source - vendor-advisory, patch

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.