How severe is CVE-2026-77504?

CVE-2026-77504 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-77504 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-77504?

CVE-2026-77504 primarily affects Microsoft Windows 10 1607. In total, 24 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-77504?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-77504 published?

CVE-2026-77504 was published on 2026-09-08 and last updated on 2026-09-29.

CVE-2026-77504

CVE-2026-77504 is a high-severity vulnerability in Microsoft Windows 10 1607 with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-415.

Key facts

Severity: High (CVSS 3.x base score 8.8)
EPSS exploit prediction: 1% (56th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-415
Affected product: Microsoft Windows 10 1607
Published: 2026-09-08
Last modified: 2026-09-29

Description

Double free in Microsoft Office Word allows an unauthorized attacker to execute code over a network.

Frequently asked questions

What is CVE-2026-77504?: Double free in Microsoft Office Word allows an unauthorized attacker to execute code over a network.
How severe is CVE-2026-77504?: CVE-2026-77504 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-77504 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-77504?: CVE-2026-77504 primarily affects Microsoft Windows 10 1607. In total, 24 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-77504?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-77504 published?: CVE-2026-77504 was published on 2026-09-08 and last updated on 2026-09-29.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-77504

Affected products (24)

cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_11_26h1:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_26h1:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:x64:*

More vulnerabilities in Microsoft Windows 10 1607

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All CVEs affecting Microsoft Windows 10 1607 →

Other CWE-415 (Double Free) vulnerabilities

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CVE-2026-84561 — Critical (CVSS 9.8): A double free issue was addressed with improved memory management. This issue is fixed in iOS 26.7 and iPadOS 26.7, iOS…
CVE-2026-77493 — Critical (CVSS 9.8): Double free in Microsoft Graphics Component allows an unauthorized attacker to execute code over a network.
CVE-2026-64387 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: smb: client: fix query directory replay…
CVE-2026-64386 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: smb: client: fix query_info() replay…

Browse all CWE-415 (Double Free) vulnerabilities →