How severe is CVE-2026-78506?

CVE-2026-78506 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-78506 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-78506?

CVE-2026-78506 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-2026-78506?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-78506 published?

CVE-2026-78506 was published on 2026-09-08 and last updated on 2026-09-17.

CVE-2026-78506

CVE-2026-78506 is a medium-severity vulnerability in Microsoft 365 Apps with a CVSS 3.x base score of 5.5. 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-170.

Key facts

Severity: Medium (CVSS 3.x base score 5.5)
EPSS exploit prediction: 1% (44th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-170
Affected product: Microsoft 365 Apps
Published: 2026-09-08
Last modified: 2026-09-17

Description

Improper null termination in Microsoft Office Word allows an unauthorized attacker to disclose information locally.

Frequently asked questions

What is CVE-2026-78506?: Improper null termination in Microsoft Office Word allows an unauthorized attacker to disclose information locally.
How severe is CVE-2026-78506?: CVE-2026-78506 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-78506 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-78506?: CVE-2026-78506 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-2026-78506?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-78506 published?: CVE-2026-78506 was published on 2026-09-08 and last updated on 2026-09-17.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78506

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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