Affects widely used Microsoft Excel; local code execution could impact many organizations.
CVE-2026-26109
Out-of-bounds read in Excel enables local code execution.
Is CVE-2026-26109 being exploited?
Not confirmed. CVE-2026-26109 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.42% probability of exploitation in the next 30 days.
How severe is CVE-2026-26109?
CVE-2026-26109 is rated High with a CVSS score of 8.4. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-26109?
Yes. A fix has been recorded for CVE-2026-26109. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-26109 affect?
CVE-2026-26109 affects Microsoft Excel, Microsoft Office Suite. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-26109?
Apply updates when released; enable Protected View; restrict macros; avoid untrusted Excel files.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Local arbitrary code execution via crafted Excel files on the victim's machine.
Patch when possible
- affected>= 16.0.1 and < https://aka.ms/OfficeSecurityReleases
- affected>= 16.0.0.0 and < 16.0.5543.1000
- affected>= 19.0.0 and < https://aka.ms/OfficeSecurityReleases
- affected>= 16.0.1 and < https://aka.ms/OfficeSecurityReleases
- affected>= 16.0.0 and < https://aka.ms/OfficeSecurityReleases
- affected>= 16.0.1 and < 16.107.26030819
- affected>= 16.0.0 and < 16.107.26030819
- affected>= 16.0.0.0 and < 16.0.10417.20102
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.