How severe is CVE-2021-31178?

CVE-2021-31178 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-2021-31178 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 16% (97th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-31178?

CVE-2021-31178 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-2021-31178?

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

When was CVE-2021-31178 published?

CVE-2021-31178 was published on 2021-05-11 and last updated on 2026-06-17.

CVE-2021-31178

CVE-2021-31178 is a medium-severity vulnerability in Microsoft 365 Apps with a CVSS 3.x base score of 5.5. Its EPSS exploit-prediction score of 16% places it in the 97th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-191.

Key facts

Severity: Medium (CVSS 3.x base score 5.5)
CVSS v2: 4.3
EPSS exploit prediction: 16% (97th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-191
Affected product: Microsoft 365 Apps
Published: 2021-05-11
Last modified: 2026-06-17

Description

Microsoft Office Information Disclosure Vulnerability

Frequently asked questions

What is CVE-2021-31178?: Microsoft Office Information Disclosure Vulnerability
How severe is CVE-2021-31178?: CVE-2021-31178 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-2021-31178 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 16% (97th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-31178?: CVE-2021-31178 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-2021-31178?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-31178 published?: CVE-2021-31178 was published on 2021-05-11 and last updated on 2026-06-17.

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31178

Affected products (13)

cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:*:*
cpe:2.3:a:microsoft:excel:2013:sp1:*:*:*:*:*:*
cpe:2.3:a:microsoft:excel:2013:sp1:*:*:rt:*:*:*
cpe:2.3:a:microsoft:excel:2016:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:office:2013:sp1:*:*:*:*:*:*
cpe:2.3:a:microsoft:office:2013:sp1:*:*:rt:*:*:*
cpe:2.3:a:microsoft:office:2016:*:*:*:*:-:*:*
cpe:2.3:a:microsoft:office:2019:*:*:*:*:-:*:*
cpe:2.3:a:microsoft:office_online_server:-:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:office_web_apps_server:2013:sp1:*:*:*:*:*:*
cpe:2.3:a:microsoft:word:2013:sp1:*:*:*:*:*:*
cpe:2.3:a:microsoft:word:2013:sp1:*:*:rt:*:*:*
cpe:2.3:a:microsoft:word:2016:*:*:*:*:*:*:*

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