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PatchSiren cyber security CVE debrief

CVE-2026-81958 Microsoft CVE debrief

Microsoft Office Excel vulnerability allows local information disclosure. The vulnerability, tracked as CVE-2026-81958, is a Use of uninitialized resource issue that can be exploited by an unauthorized attacker to disclose information locally. Defenders responsible for Microsoft Office Excel and Office installations should assess exposure and prioritize patching to prevent potential local information disclosure. The vulnerability has a CVSS score of 5.5 and a severity of MEDIUM. Affected versions of Microsoft Office Excel and Office need to be verified, and patches should be applied accordingly. Monitoring for potential local information disclosure attempts is also recommended.

Vendor
Microsoft
Product
Microsoft 365 Apps for Enterprise
CVSS
MEDIUM 5.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-08
Original CVE updated
2026-09-17
Advisory published
2026-09-08
Advisory updated
2026-09-17

Who should care

Defenders responsible for Microsoft Office Excel and Office installations should assess exposure and prioritize patching to prevent potential local information disclosure.

Why it matters

CVE-2026-81958 is a medium-severity vulnerability in Microsoft Office Excel that allows local information disclosure. Defenders should assess exposure, prioritize patching for affected Excel and Office versions, and monitor for potential local information disclosure attempts. The vulnerability requires verification of affected versions and patches.

  • Local information disclosure possible
  • Requires verification of affected versions and patches
  • Defenders need to assess exposure and prioritize patching

Technical summary

CVE-2026-81958 is a Use of uninitialized resource vulnerability in Microsoft Office Excel, allowing an unauthorized attacker to disclose information locally. The vulnerability has a CVSS score of 5.5 and a severity of MEDIUM. Affected product context includes Microsoft Office Excel installations. Defensive impact involves assessing exposure, prioritizing patching for affected Excel and Office versions, and monitoring for potential local information disclosure attempts. The vulnerability requires verification of affected versions and patches.

Defensive priority

Assess exposure, prioritize patching for Excel and Office

Recommended defensive actions

  • Inventory and assess exposure of Microsoft Office Excel installations
  • Prioritize and apply patches for affected Excel and Office versions
  • Monitor for potential local information disclosure attempts

Evidence notes

CVE-2026-81958 is a Use of uninitialized resource vulnerability in Microsoft Office Excel. The NVD entry is currently Analyzed. The vulnerability allows an unauthorized attacker to disclose information locally. The CVE record was published on 2026-09-08T18:20:59.673Z and has not been modified since then. The vulnerability has a CVSS score of 5.5 and a severity of MEDIUM. Defenders should verify affected versions and apply patches accordingly. The source detail is limited, and defenders

Sources and references

Verified primary and authoritative sources

  • CVE-2026-81958 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-81958

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

  • CVE-2026-81958 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-81958

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

Supplemental references

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.