CVE-2026-55898: Microsoft Excel Information Disclosure Vulnerability

mediumCVSS 6.1CVE-2026-55898

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

CSIRTS triage

vendor: Microsoft product: Microsoft Excel Information disclosure

What: Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.
Who is affected: Unauthorized users of Microsoft Excel.
Urgency: Remediation is necessary due to the medium severity and risk of information disclosure.
Action: Update Microsoft Excel to the latest version.

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 6.1
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55898

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-2026-558980.30% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 22% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-55898	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

critical[NEW] [critical] Microsoft Office products: Multiple vulnerabilitiescert-bund
unknownexploitedNCSC-2026-0237 [1.02] [H/H] Vulnerabilities Fixed in Microsoft Officencsc-nl
unknownexploitedNCSC-2026-0237 [1.01] [H/H] Vulnerabilities fixed in Microsoft Officencsc-nl
unknownexploitedNCSC-2026-0237 [1.00] [M/H] Vulnerabilities fixed in Microsoft Officencsc-nl
mediumCVE-2026-55898: Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose infor…nvd

Recent advisories for Microsoft Excel 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.

mediumCVE-2026-55898: Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose infor…nvd · 2026-07-14
mediumCVE-2026-55138: Untrusted pointer dereference in Microsoft Office Excel allows an unauthorized attacker to dis…nvd · 2026-07-14
highCVE-2026-55122: Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose infor…nvd · 2026-07-14
mediumCVE-2026-55054: Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose infor…nvd · 2026-07-14
mediumCVE-2026-55046: Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose infor…nvd · 2026-07-14
mediumCVE-2026-50408: Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose infor…nvd · 2026-07-14