CVE-2021-41349: Microsoft Exchange Server spoofing via crafted request

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 18 September 2026. Confidence: low.

high priorityThe CVSS score is only medium (6.5) and there is no confirmed exploitation, but the very high EPSS percentile and internet-facing Exchange target make timely patching important.

What it is

CVE-2021-41349 is a spoofing vulnerability in Microsoft Exchange Server. The record gives only a one-line description and no root-cause detail, so the exact spoofing mechanism is not documented here. It matters because Exchange is an internet-facing service and spoofing can undermine trust in mail and authentication flows.

Impact

An attacker could impersonate or spoof content or identity within Exchange, potentially deceiving users or downstream systems. The CVSS vector shows high confidentiality impact but no integrity or availability impact, which is unusual for a spoofing flaw and suggests the practical effect is information disclosure through deception.

Attack surface

Reachable over the network (AV:N) with no privileges required (PR:N), but exploitation requires user interaction (UI:R), meaning a victim must take some action such as clicking a link or opening crafted content. No authentication is needed on the attacker side per the vector.

Exploitation

Not listed in CISA KEV and no reference is tagged as exploit code, so there is no confirmed in-the-wild exploitation in this record. EPSS is very high (0.935, 99.8th percentile), indicating strong predicted likelihood of exploitation activity.

What to do

• Apply the Microsoft security update for CVE-2021-41349 from the MSRC advisory as the first action.
• Keep Exchange Server cumulative and security updates current, since this flaw is patched through the normal update channel.
• Restrict external exposure of Exchange services (OWA, ECP, Autodiscover) to reduce reachable attack surface.
• Enforce user awareness and link/attachment handling controls, since exploitation requires user interaction.
• Monitor vendor advisories for any follow-up guidance or revised severity for this CVE.

Detection

• Review Exchange and IIS logs for anomalous requests to OWA/ECP/Autodiscover endpoints around the patch window.
• Hunt for suspicious authentication or session activity that could indicate spoofed identity or content.
• Correlate user reports of deceptive emails or pages with server-side request logs.
• Track EPSS and KEV status changes for this CVE to prioritize monitoring.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.