RCE in Microsoft Excel via Untrusted Pointer Dereference
CVE-2026-20955 is a Critical remote code execution vulnerability in Microsoft Excel caused by an untrusted pointer dereference during processing of a malicious Excel file. The provided content states that exploitation requires convincing a user to open a crafted Excel document, after which code executes in the context of the logged-on user. The Preview Pane is not a valid attack vector for this issue. Microsoft rates the issue Critical with a CVSS score of 7.8.
Are you exposed to this one?
Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.
Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
13 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Critical Microsoft Excel remote code execution via maliciously crafted Office files (memory-related) per the content.
A Microsoft Excel RCE caused by untrusted pointer dereference during file parsing, enabling arbitrary code execution when a user opens a crafted spreadsheet.
A Microsoft Excel RCE caused by untrusted pointer dereference during file parsing, enabling arbitrary code execution when a user opens a crafted spreadsheet.
A severe vulnerability affecting Microsoft Office (details not provided in the content).
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.