Actively exploited · Published Jul 14, 2021 · Assigned by microsoft
CVE-2021-34523Microsoft Exchange Server Elevation of Privilege Vulnerability
Critical 9.0 Exploited Ransomware
In plain English
A critical-severity security flaw in Microsoft Exchange Server 2013 Cumulative Update 23 from Microsoft. Attackers are actively exploiting it in the wild (listed by CISA on November 3, 2021). It has been used in ransomware campaigns. The chance it is exploited in the next 30 days is estimated at 100.0% (higher than 99.9% of all known vulnerabilities). Ready-made attack tooling exists: Metasploit, public proof-of-concept code. Apply updates per vendor instructions.
Severity (CVSS 3.1)9.0Critical
Exploit odds (30 days)100.0%top 0.0% of all CVEs
Exploited in the wildYesCISA KEV since Nov 3, 2021
Attack tooling2Metasploit, Public PoC
CISA guidance
Apply updates per vendor instructions.
Federal agencies must remediate by Nov 17, 2021.
Official description
Microsoft Exchange Server Elevation of Privilege Vulnerability
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 23 | 15.00.0 – before 15.00.1497.015 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 19 | 15.01.0 – before 15.01.2176.012 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 20 | 15.01.0 – before 15.01.2242.008 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 8 | 15.02.0 – before 15.02.0792.013 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 9 | 15.02.0 – before 15.02.0858.010 |
References
- Microsoft Exchange Server Elevation of Privilege Vulnerability vendor-advisory, patch
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523 x_refsource_MISC, x_transferred
- https://www.zerodayinitiative.com/advisories/ZDI-21-822/ x_refsource_MISC, x_transferred
- http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html x_refsource_MISC, x_transferred
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523 government-resource