CVE-2021-41349 — Exchange Server
MEDIUMCVE-2021-41349 is a medium-severity (CVSS 6.5) vulnerability in microsoft exchange server. 6 public exploit references exist, so weaponization risk is real. No vendor fix is recorded yet; mitigation options are listed below.
Microsoft Exchange Server Spoofing Vulnerability
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-41349 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 397,508 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.
Description
Microsoft Exchange Server Spoofing Vulnerability
Affected Products
exchange servermicrosoftResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Vendor / applianceDetect
Inventory every microsoft exchange server deployment and check each version against the affected-products list above.
Remediation status
No patch has shipped for CVE-2021-41349 yet — track the microsoft exchange server advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
How to detect CVE-2021-41349
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2021-41349 -u https://target- Template
- Microsoft Exchange Server Pre-Auth POST Based Cross-Site Scripting
- Severity
- medium
- Impact
- Successful exploitation of this vulnerability could allow an attacker to execute arbitrary script code in the context of the targeted user's browser, potentially leading to session hijacking, data theft, or other malicious activities.
- Remediation
- Apply the latest security updates provided by Microsoft to mitigate this vulnerability.
Template by ProjectDiscovery nuclei-templates (rootxharsh, iamnoooob), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2021-41349 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.