CVE-2026-55056: Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.

This month

HIGH 7.8WATCHLISTMITIGATEMITIGATEMITIGATE

CVE-2026-55056 is a high-severity flaw (CVSS 7.8) affecting 365 apps, microsoft 365, office 2016. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.

Why this priority

High severity
On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.5% (top 60%)
CISA exploited list	No
Weakness	CWE-122, CWE-787
Published	2026-07-14
Last modified	2026-07-16

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-07-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-14 18:18 UTCPublished CVE record published
2026-07-16 14:42 UTCUpdated Record last modified

microsoft 365 apps MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy 365-apps || rpm -q 365-apps || 365-apps --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

microsoft microsoft 365 MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy microsoft-365 || rpm -q microsoft-365 || microsoft-365 --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

microsoft office 2016 MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy office-2016 || rpm -q office-2016 || office-2016 --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

microsoft office 2019 MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy office-2019 || rpm -q office-2019 || office-2019 --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

microsoft office 2021 MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy office-2021 || rpm -q office-2021 || office-2021 --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

microsoft office 2021 MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy office-2021 || rpm -q office-2021 || office-2021 --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-55056?

365 apps: mitigate or apply the listed mitigation; microsoft 365: mitigate or apply the listed mitigation; office 2016: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-55056 being exploited?

CVE-2026-55056 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-55056 affect?

CVE-2026-55056 affects 365 apps, microsoft 365, office 2016. Severity is high (CVSS 7.8). Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.

How urgent is CVE-2026-55056?

Priority 42/100. High severity; On your watchlist

Software pages

Microsoft Office vulnerabilities

Related CVEs

CVE-2026-23657 HIGH 7.8 MITIGATE DOWNGRADE Use after free in Microsoft Office Word allows an unauthorized attacker to execute code locally.
CVE-2026-32190 HIGH 8.4 MITIGATE DOWNGRADE Use after free in Microsoft Office allows an unauthorized attacker to execute code locally.
CVE-2026-32189 HIGH 7.8 MITIGATE DOWNGRADE Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
CVE-2026-32188 HIGH 7.1 MITIGATE DOWNGRADE Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.
CVE-2026-32200 HIGH 7.8 MITIGATE DOWNGRADE Use after free in Microsoft Office PowerPoint allows an unauthorized attacker to execute code locally.

References

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