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CVE-2026-55008 is a cross-site scripting vulnerability in Microsoft Exchange Server, affecting Outlook Web Access. The flaw is caused by improper neutralization of input during web page generation, allowing attacker-controlled content delivered through a crafted email to be rendered and executed as JavaScript in a victim’s browser session when the message is opened in OWA. Although classified by Microsoft as a spoofing vulnerability, available reporting indicates the issue is more accurately characterized as a stored XSS condition in the OWA interface. Microsoft assigned the vulnerability a CVSS v3.1 vector of AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H and a score of 9.6. Affected products include supported Microsoft Exchange Server 2016, Exchange Server 2019, and Exchange Server Subscription Edition builds prior to the patched versions released in July 2026.
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No public exploit code observed for this vulnerability.
9 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A high-severity stored cross-site scripting vulnerability affecting Outlook Web Access in Exchange Server, described by Microsoft as spoofing but characterized here as stored XSS that can execute JavaScript when a crafted email is viewed.
A spoofing vulnerability in Microsoft Exchange Server affecting Outlook Web Access, where a crafted malicious email can trigger JavaScript execution if a user interacts with it.
A stored cross-site scripting vulnerability in Outlook Web Access on Exchange Server, mentioned in the patch summary.
An Exchange Server cross-site scripting vulnerability called out as deserving increased attention.
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.