CVE-2021-34473: Microsoft Exchange Server Remote Code Execution Vulnerability
CVE-2021-34473 · Severity: critical · CVSS 9.8 · Exploited in the wild · Published 2021-11-03
Microsoft Exchange Server contains a Server-Side Request Forgery (SSRF) vulnerability, part of the 'ProxyShell' exploit chain, that allows an unauthenticated attacker to execute arbitrary code remotely. The vulnerability stems from improper validation of URI paths, enabling attackers to bypass authentication and access backend components.
Yes. CVE-2021-34473 is known to be exploited in the wild, first recorded on 3 November 2021. Treat it as urgent.
How severe is CVE-2021-34473?
Critical severity, with a CVSS score of 9.8, 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-2021-34473?
A patch was published on 2021-07-19: MSRC advisory updated with patch information Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2021-34473 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2021-34473?
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
2021-07-14: disclosed: NVD Published Date
2021-07-19: patched: MSRC advisory updated with patch information
2021-11-03: kev added: Added to CISA Known Exploited Vulnerabilities Catalog
2021-11-03: exploited: Reported as exploited in the wild per CISA KEV entry