Actively exploited · Published May 11, 2021 · Assigned by microsoft
CVE-2021-31207Microsoft Exchange Server Security Feature Bypass Vulnerability
Medium 6.6 Exploited Ransomware
In plain English
A medium-severity unrestricted file upload 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 99.8% (higher than 99.9% of all known vulnerabilities). Ready-made attack tooling exists: Metasploit. Apply updates per vendor instructions.
CISA guidance
Apply updates per vendor instructions.
Federal agencies must remediate by Nov 17, 2021.
Official description
Microsoft Exchange Server Security Feature Bypass Vulnerability
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 23 | 15.00.0 – before 15.00.1497.018 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 9 | 15.02.0 – before 15.02.0858.012 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 20 | 15.01.0 – before 15.01.2242.010 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 19 | 15.01.0 – before 15.01.2176.014 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 8 | 15.02.0 – before 15.02.0792.015 |
Weakness: CWE-434 · Vector: 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
References
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31207 x_refsource_MISC
- https://www.zerodayinitiative.com/advisories/ZDI-21-819/ x_refsource_MISC
- http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31207 government-resource