CVE-2021-31207
Microsoft Exchange Server Security Feature Bypass Vulnerability
Microsoft Exchange Server Security Feature Bypass Vulnerability
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- High
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Microsoft Exchange Server Security Feature Bypass Vulnerability
Microsoft Exchange Server Security Feature Bypass Vulnerability
- Record
CVE-2021-31207- CVSS 3.1
- 6.6 Medium
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - Weakness
- CWE-434
- Updated
- 2026-11-02
EUVDEUVD-2021-18120
Microsoft Exchange Server Security Feature Bypass Vulnerability
- Record
EUVD-2021-18120- CVSS 3.1
- 6.6 Medium
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-jcxv-6f65-7hrx
Microsoft Exchange Server Security Feature Bypass Vulnerability
Microsoft Exchange Server Security Feature Bypass Vulnerability
- Record
GHSA-jcxv-6f65-7hrx- CVSS 3.1
- 7.2 High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-22, CWE-434
- Updated
- 2026-11-02
CISA KEV No score
Microsoft Exchange Server Security Feature Bypass Vulnerability
Microsoft Exchange Server contains an unspecified vulnerability that allows for security feature bypass.
- Record
CVE-2021-31207- Weakness
- CWE-20, CWE-434
- Updated
- 2026-11-02
NVD
Microsoft Exchange Server Security Feature Bypass Vulnerability
- Record
CVE-2021-31207- CVSS 3.1
- 6.6 Medium
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 6.5 Medium
AV:N/AC:L/Au:S/C:P/I:P/A:P - Weakness
- CWE-434
- Updated
- 2026-11-02
Affected products
Public exploits
Links only. Every CVE stores no exploit code.
| Source | Link | Date |
|---|---|---|
| Metasploit | Microsoft Exchange ProxyShell RCE | 2021-04-06 |
History
| Recorded | Changed | Sources |
|---|---|---|
| exploitation | ||
| first indexed | CVE List, EUVD, GitHub Advisories, CISA KEV, Metasploit, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-31207 is a medium vulnerability (CVSS 6.6) in Microsoft Exchange Server, published May 11, 2021. CISA lists it as known to be exploited, since November 3, 2021. EUVD reports exploitation since November 3, 2021. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 99.8%, the 99th percentile. No source names a fixed version.
References
portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31207
zerodayinitiative.com/advisories/ZDI-21-819
packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html
cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31207
nvd.nist.gov/vuln/detail/CVE-2021-31207
github.com/advisories/GHSA-jcxv-6f65-7hrx