CVE-2026-55121: Microsoft Office Information Disclosure Vulnerability

mediumCVSS 5.5CVE-2026-55121

Out-of-bounds read in Microsoft Office allows an unauthorized attacker to disclose information locally.

CSIRTS triage

vendor: Microsoft product: Office Information disclosure

What: Out-of-bounds read in Microsoft Office allows an unauthorized attacker to disclose information locally.
Who is affected: Users of Microsoft Office are affected.
Urgency: Remediation is important due to the medium severity and potential for information disclosure.
Action: Apply the latest security patch for Microsoft Office.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 5.5
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55121

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-551210.36% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 29% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-55121	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Microsoft Office Information

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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mediumCVE-2026-70325: Improper input validation in Microsoft Office PowerPoint allows an unauthorized attacker to di…nvd · 2026-08-11
mediumCVE-2026-70323: Improper input validation in Microsoft Office allows an unauthorized attacker to disclose info…nvd · 2026-08-11
mediumCVE-2026-70322: Improper input validation in Microsoft Office PowerPoint allows an unauthorized attacker to di…nvd · 2026-08-11