{"id":49454,"date":"2025-06-07T04:44:23","date_gmt":"2025-06-07T04:44:23","guid":{"rendered":""},"modified":"2025-09-26T20:58:32","modified_gmt":"2025-09-27T02:58:32","slug":"cve-2021-47668-linux-kernel-vulnerability-leading-to-potential-system-compromise-or-data-leakage","status":"publish","type":"post","link":"https:\/\/www.ameeba.com\/blog\/cve-2021-47668-linux-kernel-vulnerability-leading-to-potential-system-compromise-or-data-leakage\/","title":{"rendered":"<strong>CVE-2021-47668: Linux Kernel Vulnerability Leading to Potential System Compromise or Data Leakage<\/strong>"},"content":{"rendered":"<p><strong>Overview<\/strong><\/p>\n<p>The Linux kernel, a crucial component that powers millions of servers and devices worldwide, has recently been found to contain a significant vulnerability, designated as CVE-2021-47668. This vulnerability pertains to a use-after-free bug in the Controller Area Network (CAN) device driver, which if exploited, could lead to system compromise or data leakage. This vulnerability is particularly concerning due to the widespread use of the <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=\"56224\">Linux kernel<\/a> in various devices and systems, from personal computers to enterprise servers, underscoring the urgent need for patching and mitigation.<\/p>\n<p><strong>Vulnerability Summary<\/strong><\/p>\n<p>CVE ID: CVE-2021-47668<br \/>\nSeverity: High (7.8 CVSS score)<br \/>\nAttack Vector: Local<br \/>\nPrivileges Required: Low<br \/>\nUser Interaction: None<br \/>\nImpact: Potential <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-41651-critical-system-compromise-due-to-missing-authentication\/\"  data-wpil-monitor-id=\"55896\">system compromise or data leakage due<\/a> to use-after-free bug in the Linux kernel.<\/p>\n<p><strong>Affected Products<\/strong><\/p><div id=\"ameeb-261443776\" 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-2025-21893-critical-linux-kernel-vulnerability-in-key-put-function\/\"  data-wpil-monitor-id=\"56817\">Linux Kernel<\/a> | Versions before the patched release<\/p>\n<p><strong>How the Exploit Works<\/strong><\/p>\n<p>The vulnerability arises from a <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-21879-the-linux-kernel-btrfs-use-after-free-vulnerability\/\"  data-wpil-monitor-id=\"56544\">use-after-free bug in the Linux kernel&#8217;s<\/a> CAN network device driver. This occurs when the kernel attempts to <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-49181-unauthorized-api-endpoint-access-leading-to-denial-of-service-and-data-leakage\/\"  data-wpil-monitor-id=\"61670\">access a data<\/a> structure (specifically, a socket buffer or skb) after it&#8217;s been freed or deallocated. In particular, a can_frame structure (cf), which aliases skb&#8217;s memory, is accessed after the netif_rx_ni() function call, <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-22040-race-condition-vulnerability-in-linux-kernel-resulting-in-potential-system-compromise\/\"  data-wpil-monitor-id=\"57850\">resulting in a potentially<\/a> unsafe dereference. This could lead to several adverse outcomes, including memory corruption, leading to a system crash or, in the worst-case scenario, <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-48828-arbitrary-php-code-execution-in-vbulletin-via-template-conditionals\/\"  data-wpil-monitor-id=\"55730\">arbitrary code execution<\/a>.<\/p>\n<p><strong>Conceptual Example Code<\/strong><\/p><div id=\"ameeb-729577474\" 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>The following pseudocode illustrates the order of operations that can <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-46458-critical-cross-site-request-forgery-csrf-vulnerability-leading-to-sql-injection-in-occupancyplan\/\"  data-wpil-monitor-id=\"55443\">lead to the vulnerability<\/a>:<\/p>\n<pre><code class=\"\" data-line=\"\">struct can_frame *cf;\nstruct sk_buff *skb;\n\/\/ Receive data\nskb = netif_rx_ni();\n\/\/ Dereference after free\ncf = (struct can_frame *)skb-&gt;data;\n\/\/ This is the problematic line - accessing cf after netif_rx_ni\nstats-&gt;rx_bytes += cf-&gt;len;<\/code><\/pre>\n<p>To mitigate the vulnerability, the code should be reordered as follows:<\/p>\n<pre><code class=\"\" data-line=\"\">struct can_frame *cf;\nstruct sk_buff *skb;\n\/\/ Dereference before free\ncf = (struct can_frame *)skb-&gt;data;\nstats-&gt;rx_bytes += cf-&gt;len;\n\/\/ Then receive data\nskb = netif_rx_ni();<\/code><\/pre>\n<p>To <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2024-49842-critical-memory-corruption-vulnerability-in-protected-vm-address-space\/\"  data-wpil-monitor-id=\"58893\">protect against this vulnerability<\/a>, users are advised to apply the latest vendor patches. In cases where immediate patching is not possible, <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-31100-unrestricted-file-upload-leads-to-web-shell-deployment-in-mojoomla-school-management\/\"  data-wpil-monitor-id=\"84692\">deploying a Web<\/a> Application Firewall (WAF) or Intrusion Detection System (IDS) can provide temporary mitigation.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Overview The Linux kernel, a crucial component that powers millions of servers and devices worldwide, has recently been found to contain a significant vulnerability, designated as CVE-2021-47668. This vulnerability pertains to a use-after-free bug in the Controller Area Network (CAN) device driver, which if exploited, could lead to system compromise or data leakage. This vulnerability [&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":[80],"asset_type":[],"severity":[],"exploit_status":[],"class_list":["post-49454","post","type-post","status-publish","format-standard","hentry","category-uncategorized","vendor-linux","product-linux-kernel","attack_vector-rce"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/49454","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=49454"}],"version-history":[{"count":10,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/49454\/revisions"}],"predecessor-version":[{"id":77477,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/49454\/revisions\/77477"}],"wp:attachment":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/media?parent=49454"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/categories?post=49454"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/tags?post=49454"},{"taxonomy":"vendor","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/vendor?post=49454"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/product?post=49454"},{"taxonomy":"attack_vector","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/attack_vector?post=49454"},{"taxonomy":"asset_type","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/asset_type?post=49454"},{"taxonomy":"severity","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/severity?post=49454"},{"taxonomy":"exploit_status","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/exploit_status?post=49454"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}