CVE-2021-21993: 
vSphere vCenter Server vulnerability analysis and mitigation

CVE-2021-21993 is a Server Side Request Forgery (SSRF) vulnerability discovered in VMware vCenter Server Content Library, disclosed in September 2021. The vulnerability affects VMware vCenter Server versions 6.5, 6.7, and 7.0, as well as VMware Cloud Foundation versions 3.x and 4.x. This vulnerability stems from improper validation of URLs in the vCenter Server Content Library (VMware Advisory).

The vulnerability has been assigned a CVSS v3.1 base score of 4.3 (Moderate severity), with the vector string AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N. The vulnerability exists due to improper validation of URLs in the vCenter Server Content Library component (NVD, VMware Advisory).

When successfully exploited, this vulnerability can lead to information disclosure. The impact is limited as it requires an authorized user with access to the content library to exploit (VMware Advisory).

VMware has released patches to address this vulnerability in the following versions: vCenter Server 7.0 U2c, 6.7 U3o, and 6.5 U3q. For Cloud Foundation, the fixes are available in versions 4.3 and 3.10.2.2. No workarounds are available, making it essential to apply the provided patches (VMware Advisory).

The vulnerability was discovered and reported independently by Osama Alaa of Malcrove and vitquay of Vantage Point Security. While this vulnerability was part of a larger security advisory that included multiple vulnerabilities in vCenter Server, it received relatively less attention due to its moderate severity rating and limited exploit potential (Hacker News).