CVE-2021-42321

HIGH8.8

CISA KEV

Published 2021-11-10 · Updated 2026-08-19 · Source secure@microsoft.com

Summary

CVE-2021-42321 is a high-severity (CVSS 8.8) vulnerability in Microsoft Exchange. CISA added it to the Known Exploited Vulnerabilities catalog on November 17, 2021, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by December 1, 2021. CISA also lists it as known to be used in ransomware campaigns, so it should be prioritised accordingly. Microsoft has 390 vulnerabilities in the KEV catalog, 117 of them linked to ransomware.

All 390 known-exploited Microsoft vulnerabilities →

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CISA Known-Exploited Vulnerability

Product: Microsoft — Exchange

Name: Microsoft Exchange Server Remote Code Execution Vulnerability

Date added: 2021-11-17 · Due: 2021-12-01

USED IN RANSOMWARE

Required action: Apply updates per vendor instructions.

References

View on NVD

More exploited Microsoft vulnerabilities

Most recently added to CISA KEV

CVE-2026-96951
Windows — Microsoft Windows Command Injection Vulnerability
added 2026-10-13
CVE-2026-65660
SharePoint — Microsoft SharePoint Code Injection Vulnerability
added 2026-09-25
CVE-2026-81963
Windows — Microsoft Windows Link Following Vulnerability
added 2026-09-08
CVE-2026-85880
Windows — Microsoft Windows Heap-Based Buffer Overflow Vulnerability
added 2026-09-08
CVE-2019-1068
SQL Server — Microsoft SQL Server Remote Code Execution Vulnerability
added 2026-08-26
CVE-2026-33824
Internet Key Exchange (IKE) Service Extensions — Microsoft Internet Key Exchange (IKE) Service Extensions Double Free Vulnerability
added 2026-08-18

View all →

Related CVEs

Same severity, most recent

CVE-2026-65960
Tetragon is an eBPF-based security observability and runtime enforcement project. Versions before 1.7.0 can use a Helm default that exposes the privileged Tetragon gRPC API through an unauthenticated TCP listener on localhost:54321. An attacker who can run or compromise same-node hostNetwork pods can reach the listener and invoke privileged methods without authentication. These methods can add, delete, or reconfigure tracing policies and change debug settings, potentially resulting in privilege escalation or container escape. Version 1.7.0 changes the default endpoint to a Unix-domain socket. Deployments that do not expose an unauthenticated TCP listener are not affected.
2026-11-06 · score 8.8
CVE-2026-33050
GeoNode is a geospatial content management system, a platform for the management and publication of geospatial data. Prior to 5.1.0, a crafted vector file layer name supplied during upload allows a low-privileged remote user to inject shell syntax and execute arbitrary operating-system commands on the GeoNode server. This issue is fixed in version 5.1.0.
2026-11-06 · score 8.8
CVE-2026-124040
CivetWeb through 1.16, when built with USE_HTTP2 and enable_http2 on, contains a use-after-free vulnerability in handle_http2() that retains freed :method and :path pointers. Unauthenticated remote attackers can send a later HEADERS frame omitting these pseudo-headers to influence request method or path seen by access rules, or crash the server.
2026-11-06 · score 8.1
CVE-2026-124027
ChatWiki before 2.10.0 contains a missing authentication vulnerability in the GET /manage/getLibRawFileOnePage route that allows unauthenticated attackers to read other tenants' documents. Attackers can enumerate sequential admin_user_id and file id query parameters, bypassing the ownership check, to retrieve PDF-rendered pages of any tenant's knowledge-base documents.
2026-11-06 · score 7.5
CVE-2026-123974
In all versions of PyTorch's TorchServe, a predictable extraction directory in /tmp lets a local user swap the model handler and run code as the TorchServe service account leading to local privilege escalation.
2026-11-06 · score 7.8