How severe is CVE-2026-77901?

CVE-2026-77901 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-2026-77901 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-2026-77901?

CVE-2026-77901 primarily affects Microsoft 365 Apps. In total, 13 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-77901?

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-2026-77901 published?

CVE-2026-77901 was published on 2026-09-08 and last updated on 2026-09-17.

CVE-2026-77901

CVE-2026-77901 is a high-severity vulnerability in Microsoft 365 Apps 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-476.

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-476
Affected product: Microsoft 365 Apps
Published: 2026-09-08
Last modified: 2026-09-17

Description

Null pointer dereference in Microsoft Office Word allows an unauthorized attacker to execute code over a network.

Frequently asked questions

What is CVE-2026-77901?: Null pointer dereference in Microsoft Office Word allows an unauthorized attacker to execute code over a network.
How severe is CVE-2026-77901?: CVE-2026-77901 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-2026-77901 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-2026-77901?: CVE-2026-77901 primarily affects Microsoft 365 Apps. In total, 13 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-77901?: 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-2026-77901 published?: CVE-2026-77901 was published on 2026-09-08 and last updated on 2026-09-17.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-77901

Affected products (13)

cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x64:*
cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x86:*
cpe:2.3:a:microsoft:microsoft_365:-:*:*:*:*:macos:*:*
cpe:2.3:a:microsoft:office_2019:-:*:*:*:*:*:x64:*
cpe:2.3:a:microsoft:office_2019:-:*:*:*:*:*:x86:*
cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x64:*
cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x86:*
cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:macos:-:*
cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x64:*
cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x86:*
cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:macos:-:*
cpe:2.3:a:microsoft:word:2016:*:*:*:*:*:x64:*
cpe:2.3:a:microsoft:word:2016:*:*:*:*:*:x86:*

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