{"id":27884,"date":"2021-11-10T16:36:00","date_gmt":"2021-11-10T15:36:00","guid":{"rendered":"https:\/\/perseus.de\/zero-day-vulnerabilities-discovered-at-microsoft-again\/"},"modified":"2026-03-31T07:31:00","modified_gmt":"2026-03-31T05:31:00","slug":"zero-day-vulnerabilities-discovered-at-microsoft-again","status":"publish","type":"post","link":"https:\/\/perseus.de\/en\/zero-day-vulnerabilities-discovered-at-microsoft-again\/","title":{"rendered":"Zero-day vulnerabilities discovered at Microsoft again"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"27884\" class=\"elementor elementor-27884 elementor-22966\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-dcf4ec4 e-flex e-con-boxed e-con e-parent\" data-id=\"dcf4ec4\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-e1db58c elementor-widget elementor-widget-image\" data-id=\"e1db58c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"800\" height=\"200\" src=\"https:\/\/perseus.de\/wp-content\/uploads\/2025\/04\/Gefahrenwarnung-Headerbild-Website-2025-1024x256.png\" class=\"attachment-large size-large wp-image-27799\" alt=\"\" srcset=\"https:\/\/perseus.de\/wp-content\/uploads\/2025\/04\/Gefahrenwarnung-Headerbild-Website-2025-1024x256.png 1024w, https:\/\/perseus.de\/wp-content\/uploads\/2025\/04\/Gefahrenwarnung-Headerbild-Website-2025-300x75.png 300w, https:\/\/perseus.de\/wp-content\/uploads\/2025\/04\/Gefahrenwarnung-Headerbild-Website-2025-768x192.png 768w, https:\/\/perseus.de\/wp-content\/uploads\/2025\/04\/Gefahrenwarnung-Headerbild-Website-2025.png 1200w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-1258a43 e-flex e-con-boxed e-con e-parent\" data-id=\"1258a43\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t<div class=\"elementor-element elementor-element-2de4e88 e-con-full e-flex e-con e-child\" data-id=\"2de4e88\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-4982c80 elementor-widget elementor-widget-text-editor\" data-id=\"4982c80\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h6>10.11.2021<\/h6>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-8348bc5 elementor-widget elementor-widget-heading\" data-id=\"8348bc5\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Zero-day vulnerabilities discovered at Microsoft again\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-eb03842 e-con-full e-flex e-con e-child\" data-id=\"eb03842\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-91d0988 elementor-widget elementor-widget-text-editor\" data-id=\"91d0988\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><strong>Due to zero-day security vulnerabilities for Microsoft Exchance Server, among others, there is a threat of a new wave of attacks on unpatched Microsoft Exchange servers. Below you will find further background information and information on how to deal with the attack. <\/strong><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-f85a5ad e-flex e-con-boxed e-con e-parent\" data-id=\"f85a5ad\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t<div class=\"elementor-element elementor-element-fad2031 e-con-full e-flex e-con e-child\" data-id=\"fad2031\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-8282d30 elementor-widget elementor-widget-text-editor\" data-id=\"8282d30\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><strong>What happened?<\/strong><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-ee744d2 e-con-full e-flex e-con e-child\" data-id=\"ee744d2\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-5ea6506 elementor-widget elementor-widget-text-editor\" data-id=\"5ea6506\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>On November 9, 2021,<a href=\"https:\/\/threatpost.com\/microsoft-nov-patch-tuesday-fixes-six-zero-days-55-bugs\/176143\/\"> 55 patches were released for Microsoft<\/a>, six of which are critical. In February and March, zero-day vulnerabilities in Microsoft Exchange servers were exploited by attackers to gain access to servers. Currently, two zero-day vulnerabilities have been discovered again, one of them for Microsoft Exchange Server.  <\/p><p>The <a href=\"https:\/\/krebsonsecurity.com\/2021\/11\/microsoft-patch-tuesday-november-2021-edition\/\">CVE-2021-42321 zero-day vulnerability<\/a> is located in Microsoft Exchange servers and requires immediate action as it is already being actively exploited by attackers. The Perseus cybersecurity team strongly advises you to install the available security patches immediately. <\/p><p>The <a href=\"https:\/\/krebsonsecurity.com\/2021\/11\/microsoft-patch-tuesday-november-2021-edition\/\">CVE-2021-42292 vulnerability<\/a> makes it possible to bypass the security features in Microsoft Excel versions 2013-2021. Attackers could thus install malicious code. All you have to do is get users to download manipulated Excel files \u2013 for example, through phishing emails.  <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-f1dfa8e e-flex e-con-boxed e-con e-parent\" data-id=\"f1dfa8e\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-bf4f09a elementor-widget-divider--view-line elementor-widget elementor-widget-divider\" data-id=\"bf4f09a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"divider.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-divider\">\n\t\t\t<span class=\"elementor-divider-separator\">\n\t\t\t\t\t\t<\/span>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-a82985c e-flex e-con-boxed e-con e-parent\" data-id=\"a82985c\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t<div class=\"elementor-element elementor-element-482032b e-con-full e-flex e-con e-child\" data-id=\"482032b\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-b5f6a5c elementor-widget elementor-widget-text-editor\" data-id=\"b5f6a5c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><strong>CVE-2021-42321: By experts for experts<\/strong><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-8f5d6ed e-con-full e-flex e-con e-child\" data-id=\"8f5d6ed\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-057f5b5 elementor-widget elementor-widget-text-editor\" data-id=\"057f5b5\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>The CVE-2021-42321 zero-day vulnerability is a critical remote code execution (RCE) vulnerability in Exchange Server caused by issues with the validation of commandlet arguments (cmdlet) \u2013 that is, lightweight commands used in the PowerShell environment. They are invoked by the PowerShell runtime in the context of automation scripts deployed from the command line or programmatically invoked by the PowerShell runtime through APIs. <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-6237d73 e-flex e-con-boxed e-con e-parent\" data-id=\"6237d73\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-9dde6dc elementor-widget-divider--view-line elementor-widget elementor-widget-divider\" data-id=\"9dde6dc\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"divider.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-divider\">\n\t\t\t<span class=\"elementor-divider-separator\">\n\t\t\t\t\t\t<\/span>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-02dd0e9 e-flex e-con-boxed e-con e-parent\" data-id=\"02dd0e9\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t<div class=\"elementor-element elementor-element-16d621d e-con-full e-flex e-con e-child\" data-id=\"16d621d\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-89904c7 elementor-widget elementor-widget-text-editor\" data-id=\"89904c7\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><strong>What are the dangers for your company?<\/strong><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-fae461d e-con-full e-flex e-con e-child\" data-id=\"fae461d\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-0f04793 elementor-widget elementor-widget-text-editor\" data-id=\"0f04793\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>The vulnerabilities are already being exploited by cybercriminals. They allow the attackers to implant webshells and perform remote command executions, in short: actively execute commands on the compromised computers to install malware or ransomware and spy on sensitive data. For example, reply emails are sent from personal accounts that contain malicious links.  <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-cdadbd8 e-flex e-con-boxed e-con e-parent\" data-id=\"cdadbd8\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-104dd95 elementor-widget-divider--view-line elementor-widget elementor-widget-divider\" data-id=\"104dd95\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"divider.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-divider\">\n\t\t\t<span class=\"elementor-divider-separator\">\n\t\t\t\t\t\t<\/span>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-f6e5251 e-flex e-con-boxed e-con e-parent\" data-id=\"f6e5251\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t<div class=\"elementor-element elementor-element-f1cf26c e-con-full e-flex e-con e-child\" data-id=\"f1cf26c\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-ee082fd elementor-widget elementor-widget-text-editor\" data-id=\"ee082fd\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><strong>What can I do?<\/strong><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-bc25934 e-con-full e-flex e-con e-child\" data-id=\"bc25934\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-2b46b6f elementor-widget elementor-widget-text-editor\" data-id=\"2b46b6f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<ul><li>Microsoft has released <a href=\"https:\/\/msrc.microsoft.com\/update-guide\/vulnerability\/CVE-2021-42321\">four patches classified as important<\/a> to fix the vulnerabilities. Check if this patch is already installed on your Microsoft Exchange Server. If not, do so immediately. Due to the speed of spread, the speed of this implementation is crucial to avoid major and cumulative cyber damage.   <\/li><li>Keep your system up to date. We recommend using all automatic updates. <\/li><\/ul>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>10.11.2021 Zero-day vulnerabilities discovered at Microsoft again Due to zero-day security vulnerabilities for Microsoft Exchance Server, among others, there is a threat of a new wave of attacks on unpatched Microsoft Exchange servers. Below you will find further background information and information on how to deal with the attack. What happened? On November 9, 2021, [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[64],"tags":[],"class_list":["post-27884","post","type-post","status-publish","format-standard","hentry","category-hazard-warning"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.3 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Zero-day vulnerabilities discovered at Microsoft again - Perseus Technologies<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/perseus.de\/en\/zero-day-vulnerabilities-discovered-at-microsoft-again\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Zero-day vulnerabilities discovered at Microsoft again - Perseus Technologies\" \/>\n<meta property=\"og:description\" content=\"10.11.2021 Zero-day vulnerabilities discovered at Microsoft again Due to zero-day security vulnerabilities for Microsoft Exchance Server, among others, there is a threat of a new wave of attacks on unpatched Microsoft Exchange servers. Below you will find further background information and information on how to deal with the attack. What happened? 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Below you will find further background information and information on how to deal with the attack. What happened? On November 9, 2021, [&hellip;]","og_url":"https:\/\/perseus.de\/en\/zero-day-vulnerabilities-discovered-at-microsoft-again\/","og_site_name":"Perseus Technologies","article_published_time":"2021-11-10T15:36:00+00:00","article_modified_time":"2026-03-31T05:31:00+00:00","og_image":[{"width":1200,"height":300,"url":"https:\/\/perseus.de\/wp-content\/uploads\/2025\/04\/Gefahrenwarnung-Headerbild-Website-2025.png","type":"image\/png"}],"author":"Xenia Silbe","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Xenia Silbe","Est. reading time":"2 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/perseus.de\/en\/zero-day-vulnerabilities-discovered-at-microsoft-again\/#article","isPartOf":{"@id":"https:\/\/perseus.de\/en\/zero-day-vulnerabilities-discovered-at-microsoft-again\/"},"author":{"name":"Xenia Silbe","@id":"https:\/\/perseus.de\/#\/schema\/person\/42cdb0ff9720a4c92a2613f686b32f46"},"headline":"Zero-day vulnerabilities discovered at Microsoft again","datePublished":"2021-11-10T15:36:00+00:00","dateModified":"2026-03-31T05:31:00+00:00","mainEntityOfPage":{"@id":"https:\/\/perseus.de\/en\/zero-day-vulnerabilities-discovered-at-microsoft-again\/"},"wordCount":373,"commentCount":0,"publisher":{"@id":"https:\/\/perseus.de\/#organization"},"image":{"@id":"https:\/\/perseus.de\/en\/zero-day-vulnerabilities-discovered-at-microsoft-again\/#primaryimage"},"thumbnailUrl":"https:\/\/perseus.de\/wp-content\/uploads\/2025\/04\/Gefahrenwarnung-Headerbild-Website-2025-1024x256.png","articleSection":["Hazard warning"],"inLanguage":"en-US","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/perseus.de\/en\/zero-day-vulnerabilities-discovered-at-microsoft-again\/#respond"]}]},{"@type":"WebPage","@id":"https:\/\/perseus.de\/en\/zero-day-vulnerabilities-discovered-at-microsoft-again\/","url":"https:\/\/perseus.de\/en\/zero-day-vulnerabilities-discovered-at-microsoft-again\/","name":"Zero-day vulnerabilities discovered at Microsoft again - 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