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CVE-2026-45491 Microsoft CVE debrief

CVE-2026-45491 is a MEDIUM severity vulnerability in .NET that allows an unauthorized attacker to perform tampering locally. The vulnerability is caused by improper link resolution before file access, also known as 'link following'. This vulnerability was published on June 9, 2026, and was modified on June 17, 2026. .NET versions 8.0.0 to 8.0.28, 9.0.0 to 9.0.17, and 10.0.0 to 10.0.9 are affected. Users should update to the latest version to mitigate this vulnerability.

Vendor
Microsoft
Product
.NET 10.0
CVSS
MEDIUM 6.2
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-09
Original CVE updated
2026-06-17
Advisory published
2026-06-09
Advisory updated
2026-06-17

Who should care

Developers and administrators using .NET versions 8.0.0 to 8.0.28, 9.0.0 to 9.0.17, and 10.0.0 to 10.0.9 should be aware of this vulnerability and take necessary actions to mitigate it.

Technical summary

The vulnerability is caused by improper link resolution before file access in .NET. This allows an unauthorized attacker to perform tampering locally. The CVSS score for this vulnerability is 6.2, with a severity of MEDIUM. The vulnerability is classified under CWE-59.

Defensive priority

MEDIUM

Recommended defensive actions

  • Update .NET to the latest version
  • Review and update vulnerable .NET applications
  • Implement secure coding practices to prevent link following vulnerabilities
  • Monitor .NET applications for suspicious activity
  • Consider implementing additional security measures such as access controls and file system monitoring
  • Review and update incident response plans to address potential tampering attacks

Evidence notes

The information provided is based on the CVE record and NVD detail for CVE-2026-45491. The vulnerability is confirmed to exist in .NET versions 8.0.0 to 8.0.28, 9.0.0 to 9.0.17, and 10.0.0 to 10.0.9.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-45491 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-45491

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

  • CVE-2026-45491 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-45491

    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.