CVE-2021-34523
Microsoft Exchange Server Elevation of Privilege Vulnerability
Microsoft Exchange Server Elevation of Privilege Vulnerability
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Microsoft Exchange Server Elevation of Privilege Vulnerability
Microsoft Exchange Server Elevation of Privilege Vulnerability
- Record
CVE-2021-34523- CVSS 3.1
- 9.0 Critical
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N/E:U/RL:O/RC:C - Updated
- 2026-11-02
EUVDEUVD-2021-21177
Microsoft Exchange Server Elevation of Privilege Vulnerability
- Record
EUVD-2021-21177- CVSS 3.1
- 9.0 Critical
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N/E:U/RL:O/RC:C - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-gcrr-725q-f8jw
Microsoft Exchange Server Elevation of Privilege Vulnerability This CVE ID is unique from CVE...
Microsoft Exchange Server Elevation of Privilege Vulnerability This CVE ID is unique from CVE-2021-33768, CVE-2021-34470.
- Record
GHSA-gcrr-725q-f8jw- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-269, CWE-287
- Updated
- 2026-11-02
CISA KEV No score
Microsoft Exchange Server Privilege Escalation Vulnerability
Microsoft Exchange Server contains an unspecified vulnerability that allows for privilege escalation.
- Record
CVE-2021-34523- Weakness
- CWE-287
- Updated
- 2026-11-02
NVD
Microsoft Exchange Server Elevation of Privilege Vulnerability
- Record
CVE-2021-34523- CVSS 3.1
- 9.0 Critical
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N - CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 7.5 High
AV:N/AC:L/Au:N/C:P/I:P/A:P - 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 |
| PoC in GitHub | mithridates1313/ProxyShell_POC | 2021-10-02 |
| PoC in GitHub | SUPRAAA-1337/CVE-2021-34523 | 2023-09-02 |
History
| Recorded | Changed | Sources |
|---|---|---|
| exploitation, exploits | ||
| first indexed | CVE List, EUVD, GitHub Advisories, CISA KEV, Metasploit, NVD, PoC in GitHub |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-34523 is a critical vulnerability (CVSS 9.0) in Microsoft Exchange Server, published July 14, 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 100.0%, the 99th percentile. No source names a fixed version.
References
msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34523
portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523
zerodayinitiative.com/advisories/ZDI-21-822
packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html
cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523
nvd.nist.gov/vuln/detail/CVE-2021-34523
github.com/advisories/GHSA-gcrr-725q-f8jw