CVE-2021-31207: Microsoft Exchange Server Security Feature Bypass Vulnerability
CVE-2021-31207 · Severity: critical · CVSS 6.6 · Exploited in the wild · Published 2021-11-03
Microsoft Exchange Server contains a security feature bypass vulnerability due to unrestricted upload of files with dangerous types (CWE-434). This vulnerability is part of the 'ProxyShell' exploit chain and allows an authenticated attacker with high privileges to bypass security restrictions.
Yes. CVE-2021-31207 is known to be exploited in the wild, first recorded on 3 November 2021. Treat it as urgent.
How severe is CVE-2021-31207?
Critical severity, with a CVSS score of 6.6, published 3 November 2021.
Which products and versions are affected?
Microsoft Exchange Server 2013 Cumulative Update 23; Microsoft Exchange Server 2016 Cumulative Update 19, Cumulative Update 20; Microsoft Exchange Server 2019 Cumulative Update 8, Cumulative Update 9.
Is there a fix for CVE-2021-31207?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2021-31207 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2021-31207?
Check whether you run Microsoft Exchange Server. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Affected products
Microsoft Exchange Server 2013 Cumulative Update 23
Microsoft Exchange Server 2016 Cumulative Update 19, Cumulative Update 20
Microsoft Exchange Server 2019 Cumulative Update 8, Cumulative Update 9
Timeline
2021-05-11: disclosed: NVD Published Date
2021-11-03: kev added: Added to CISA Known Exploited Vulnerabilities Catalog
2021-11-03: exploited: Reported as exploited in the wild in the advisory summary and CISA KEV catalog.