{"id":49459,"date":"2025-06-07T05:44:39","date_gmt":"2025-06-07T05:44:39","guid":{"rendered":""},"modified":"2025-06-10T17:52:54","modified_gmt":"2025-06-10T23:52:54","slug":"cve-2021-47669-linux-kernel-vulnerability-allowing-potential-system-compromise","status":"publish","type":"post","link":"https:\/\/www.ameeba.com\/blog\/cve-2021-47669-linux-kernel-vulnerability-allowing-potential-system-compromise\/","title":{"rendered":"<strong>CVE-2021-47669: Linux Kernel Vulnerability Allowing Potential System Compromise<\/strong>"},"content":{"rendered":"<p><strong>Overview<\/strong><\/p>\n<p>The Linux kernel, core to the operating system and responsible for managing system resources, has recently been identified with a significant vulnerability, CVE-2021-47669. This flaw resides in the Virtual eXtended CAN (vxcan) transmission process and is classified as a &#8216;use after free&#8217; bug. This vulnerability is of particular concern to Linux users and <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-41651-critical-system-compromise-due-to-missing-authentication\/\"  data-wpil-monitor-id=\"56127\">system administrators due<\/a> to the far-reaching implications of any potential exploitation. Given the Linux kernel&#8217;s ubiquity in various devices ranging from servers, personal computers, to embedded systems, this vulnerability could <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-32309-potential-system-compromise-due-to-remote-file-inclusion-in-php-program\/\"  data-wpil-monitor-id=\"56230\">potentially impact a vast number of systems<\/a> globally.<\/p>\n<p><strong>Vulnerability Summary<\/strong><\/p>\n<p>CVE ID: CVE-2021-47669<br \/>\nSeverity: High (7.8 CVSS Score)<br \/>\nAttack Vector: Network<br \/>\nPrivileges Required: Low<br \/>\nUser Interaction: None<br \/>\nImpact: Potential system compromise or <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-48383-django-select2-vulnerability-risking-data-leakage-and-unauthorized-access\/\"  data-wpil-monitor-id=\"56126\">data leakage<\/a><\/p>\n<p><strong>Affected Products<\/strong><\/p><div id=\"ameeb-2945435526\" class=\"ameeb-content-2 ameeb-entity-placement\"><div style=\"border-left: 4px solid #555; padding-left: 20px; margin: 48px 0; font-family: Roboto, sans-serif; color: #ffffff; line-height: 1.6; max-width: 700px;\">\r\n  <h2 style=\"margin-top: 0; font-size: 20px; font-weight: 600; display: flex; align-items: center;\">\r\n    <a href=\"https:\/\/www.ameeba.com\/chat\" style=\"display: inline-flex; align-items: center; margin-right: 8px;\">\r\n      <img decoding=\"async\" src=\"https:\/\/www.ameeba.com\/blog\/wp-content\/uploads\/2025\/10\/Best-App-icon-Ameeba.png\" alt=\"Ameeba Chat Icon\" style=\"width: 40px; height: 40px;\" \/>\r\n    <\/a>\r\n    A new way to communicate\r\n  <\/h2>\r\n\r\n  <p style=\"margin-bottom: 12px;\">\r\n    Ameeba Chat is built on encrypted identity, not personal profiles.\r\n  <\/p>\r\n\r\n  <p style=\"margin-bottom: 16px;\">\r\n    Message, call, share files, and coordinate with identities kept separate.\r\n  <\/p>\r\n\r\n  <ul style=\"list-style: none; padding-left: 0; margin-bottom: 20px;\">\r\n    <li>\u2022 Encrypted identity<\/li>\r\n    <li>\u2022 Ameeba Chat authenticates access<\/li>\r\n    <li>\u2022 Aliases and categories<\/li>\r\n    <li>\u2022 End-to-end encrypted chat, calls, and files<\/li>\r\n    <li>\u2022 Secure notes for sensitive information<\/li>\r\n  <\/ul>\r\n\r\n  <p style=\"font-style: italic; font-weight: 600; margin-bottom: 24px;\">\r\n    Private communication, rethought.\r\n  <\/p>\r\n\r\n  <div style=\"display: flex; flex-wrap: wrap; gap: 12px;\">\r\n    <a href=\"https:\/\/www.ameeba.com\/chat\/download\" style=\"background-color: #ffffff; color: #000000; padding: 10px 20px; text-decoration: none; border-radius: 6px; font-weight: 500;\">Download Ameeba Chat<\/a>\r\n    <a href=\"https:\/\/www.ameeba.com\/chat\" style=\"border: 1px solid #ffffff; color: #ffffff; padding: 10px 20px; text-decoration: none; border-radius: 6px; font-weight: 500;\">Learn More<\/a>\r\n  <\/div>\r\n<\/div>\r\n<\/div>\n<p>Product | Affected Versions<\/p>\n<p><a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-21879-the-linux-kernel-btrfs-use-after-free-vulnerability\/\"  data-wpil-monitor-id=\"56547\">Linux Kernel<\/a> | [All versions prior to the patch]<\/p>\n<p><strong>How the Exploit Works<\/strong><\/p>\n<p>The <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-21893-critical-linux-kernel-vulnerability-in-key-put-function\/\"  data-wpil-monitor-id=\"56814\">vulnerability occurs in the vxcan_xmit function of the Linux kernel&#8217;s<\/a> Virtual eXtended CAN. The issue arises when the function calls netif_rx_ni(skb), after which dereferencing skb becomes unsafe. Particularly, the canfd_frame cfd, which aliases skb memory, is accessed after the netif_rx_ni call. Successful exploitation of this bug could lead to unauthorized information disclosure, modification, or <a href=\"https:\/\/www.ameeba.com\/blog\/sentinelone-services-disruption-an-in-depth-analysis-of-the-recent-cybersecurity-incident\/\"  data-wpil-monitor-id=\"55547\">disruption of service<\/a>.<\/p>\n<p><strong>Conceptual Example Code<\/strong><\/p><div id=\"ameeb-3453291157\" class=\"ameeb-content ameeb-entity-placement\"><div class=\"poptin-embedded\" data-id=\"f6b387694f681\"><\/div>\r\n\r\n\r\n\r\n\r\n\r\n<\/div>\n<p>While the exact exploitation method is dependent on the specific configuration and use case of the <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-5100-a-double-free-vulnerability-leading-to-potential-system-compromise\/\"  data-wpil-monitor-id=\"56591\">vulnerable system<\/a>, conceptually a malicious actor might exploit this vulnerability through network packets that cause the kernel to dereference a freed skb object, leading to unexpected behavior or even system compromise. This could be conceptually illustrated with the following pseudocode:<\/p>\n<pre><code class=\"\" data-line=\"\">\/\/ Create malicious packet\nstruct sk_buff *skb = alloc_skb(...);\n...\n\/\/ Fill skb with malicious data\n...\n\/\/ Send packet to vulnerable system\nsend_to_vulnerable_system(skb);\n\/\/ Free skb, but it will be used later in vxcan_xmit\nkfree_skb(skb);<\/code><\/pre>\n<p><strong>Mitigation Guidance<\/strong><\/p>\n<p>The most reliable way to mitigate this vulnerability is by applying the vendor patch. Until the patch can be applied, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can offer temporary protection by monitoring and potentially blocking <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-1277-memory-corruption-vulnerability-in-autodesk-applications-through-malicious-pdf-files\/\"  data-wpil-monitor-id=\"57149\">malicious network traffic that attempts to exploit this vulnerability<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Overview The Linux kernel, core to the operating system and responsible for managing system resources, has recently been identified with a significant vulnerability, CVE-2021-47669. This flaw resides in the Virtual eXtended CAN (vxcan) transmission process and is classified as a &#8216;use after free&#8217; bug. This vulnerability is of particular concern to Linux users and system [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"footnotes":""},"categories":[1],"tags":[],"vendor":[88],"product":[95],"attack_vector":[],"asset_type":[],"severity":[],"exploit_status":[],"class_list":["post-49459","post","type-post","status-publish","format-standard","hentry","category-uncategorized","vendor-linux","product-linux-kernel"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/49459","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/comments?post=49459"}],"version-history":[{"count":7,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/49459\/revisions"}],"predecessor-version":[{"id":50996,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/49459\/revisions\/50996"}],"wp:attachment":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/media?parent=49459"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/categories?post=49459"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/tags?post=49459"},{"taxonomy":"vendor","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/vendor?post=49459"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/product?post=49459"},{"taxonomy":"attack_vector","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/attack_vector?post=49459"},{"taxonomy":"asset_type","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/asset_type?post=49459"},{"taxonomy":"severity","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/severity?post=49459"},{"taxonomy":"exploit_status","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/exploit_status?post=49459"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}