CVE-2021-31196 — Exchange Server
HIGHCVE-2021-31196 is a high-severity (CVSS 7.2) remote code execution vulnerability in microsoft exchange server. It is in CISA's Known Exploited Vulnerabilities catalog (added 2024-08-21) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.
Microsoft Exchange Server Remote Code Execution Vulnerability
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2024-08-21. Federal agencies were required to remediate by 2024-09-11.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-31196.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-31196 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).
Where this sits among everything scored
Of 395,249 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.
Description
Microsoft Exchange Server Remote Code Execution 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-2021-31196 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.
Frequently Asked Questions
Is CVE-2021-31196 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.