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CVE-2026-77491 Microsoft CVE debrief

CVE-2026-77491 is a MEDIUM severity vulnerability in Windows GDI that allows an unauthorized attacker to disclose information locally. The CVE record was published on 2026-09-08T18:20:34.830Z and has not been modified since then. The NVD entry is currently Analyzed. This vulnerability is an out-of-bounds read in Windows GDI, which could allow an attacker to disclose information locally. The CVSS score is 5.5, with a vector of CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N. Affected systems include various versions of Windows 10, Windows 11, and Windows Server. Defenders should prioritize verifying exposure in Windows environments, especially those with unpatched systems, and assess

Vendor
Microsoft
Product
Windows 10 Version 1607
CVSS
MEDIUM 5.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-08
Original CVE updated
2026-09-16
Advisory published
2026-09-08
Advisory updated
2026-09-16

Who should care

Defenders responsible for Windows environments, especially those with unpatched systems, should assess exposure and prioritize patching. They should also verify the vulnerability's impact on sensitive data and review relevant monitoring, detection, and logs for exposed assets that need extra review.

Why it matters

CVE-2026-77491 is a MEDIUM severity vulnerability in Windows GDI that allows an unauthorized attacker to disclose information locally. Defenders should prioritize verifying exposure in Windows environments, especially those with unpatched systems, and assess the impact of potential local information disclosure.

  • Verify exposure in Windows environments to prevent potential local information disclosure.
  • Assess the impact of potential local information disclosure on sensitive data.
  • Prioritize patching for affected Windows versions to prevent exploitation.

Technical summary

The vulnerability is an out-of-bounds read in Windows GDI, which could allow an attacker to disclose information locally. The CVSS score is 5.5, with a vector of CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N. Affected systems include various versions of Windows 10, Windows 11, and Windows Server.

Defensive priority

Defenders should prioritize verifying exposure in Windows environments, especially those with unpatched systems.

Recommended defensive actions

  • Verify exposure in Windows environments, especially those with unpatched systems.
  • Assess the impact of potential local information disclosure.
  • Prioritize patching for affected Windows versions.

Evidence notes

The vulnerability is described as an out-of-bounds read in Windows GDI, which could allow an attacker to disclose information locally. The CVSS score is 5.5, with a vector of CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N. Affected systems include various versions of Windows 10, Windows 11, and Windows Server.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-77491 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-77491

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

  • CVE-2026-77491 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-77491

    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.