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CVE-2026-55007 is a double-free vulnerability in Microsoft Exchange Server that allows unauthenticated remote code execution. A specially crafted Visio attachment sent by an attacker can be processed by Exchange Server during content indexing, triggering the memory-management flaw. Exploitation does not require a recipient to open the message or otherwise interact with it. Microsoft Exchange Server 2016, Exchange Server 2019, and Exchange Server Subscription Edition deployments are affected by the September 2026 update coverage.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
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.
13 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A remote-code-execution vulnerability in Microsoft Exchange Server.
A Microsoft Exchange Server remote-code-execution vulnerability that can be triggered by processing an email containing a malicious Visio attachment.
A critical unauthenticated Microsoft Exchange Server remote-code-execution flaw involving processing of a crafted Visio email attachment during content indexing. Exploitation requires sustained low-memory conditions and is described as difficult to trigger reliably.
A double-free vulnerability in Microsoft Exchange Server that enables remote code execution.
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.