{"id":48677,"date":"2025-06-04T04:10:55","date_gmt":"2025-06-04T04:10:55","guid":{"rendered":""},"modified":"2025-08-29T16:42:15","modified_gmt":"2025-08-29T22:42:15","slug":"cve-2025-21893-critical-linux-kernel-vulnerability-in-key-put-function","status":"publish","type":"post","link":"https:\/\/www.ameeba.com\/blog\/cve-2025-21893-critical-linux-kernel-vulnerability-in-key-put-function\/","title":{"rendered":"<strong>CVE-2025-21893: Critical Linux Kernel Vulnerability in key_put() Function<\/strong>"},"content":{"rendered":"<p><strong>Overview<\/strong><\/p>\n<p>The Linux kernel, a key component of many global server infrastructures, has been found to contain a critical vulnerability in its key management subsystem. The vulnerability, tracked as CVE-2025-21893, pertains to the &#8216;key_put()&#8217; function, which is responsible for reducing a key&#8217;s reference count. When mishandled, this can lead to the premature destruction of keys and consequently, <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=\"56552\">potential system compromise<\/a> or data leakage. Given the widespread adoption of Linux-based systems, this <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-46490-puzzling-vulnerability-in-crossword-compiler-puzzles-risks-system-compromise\/\"  data-wpil-monitor-id=\"54604\">vulnerability poses a significant risk<\/a> to organizations and their data, making immediate mitigation a top priority.<\/p>\n<p><strong>Vulnerability Summary<\/strong><\/p>\n<p>CVE ID: CVE-2025-21893<br \/>\nSeverity: High (7.8 CVSS Score)<br \/>\nAttack Vector: Network<br \/>\nPrivileges Required: Low<br \/>\nUser Interaction: None<br \/>\nImpact: <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-5100-a-double-free-vulnerability-leading-to-potential-system-compromise\/\"  data-wpil-monitor-id=\"56782\">Potential system<\/a> compromise or data leakage<\/p>\n<p><strong>Affected Products<\/strong><\/p><div id=\"ameeb-4278158488\" 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=\"56551\">Linux Kernel<\/a> | Versions prior to patch release<\/p>\n<p><strong>How the Exploit Works<\/strong><\/p>\n<p>The <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-21999-use-after-free-vulnerability-in-linux-kernel\/\"  data-wpil-monitor-id=\"56834\">vulnerability at hand concerns the use-after-free<\/a> (UAF) flaw in the &#8216;key_put()&#8217; function of the Linux kernel. This function, responsible for reducing a key&#8217;s reference count, can <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2021-47668-linux-kernel-vulnerability-leading-to-potential-system-compromise-or-data-leakage\/\"  data-wpil-monitor-id=\"57516\">potentially lead<\/a> to the key&#8217;s premature destruction once its count reaches zero. The garbage collector thread may destroy the key at any point after this, making any subsequent touches on the <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-26476-unauthorized-access-by-use-of-hard-coded-cryptographic-key-in-dell-ecs-and-objectscale\/\"  data-wpil-monitor-id=\"74065\">key unauthorized<\/a>. However, to speed up quota reclamation, the key is looked at in &#8216;key_put()&#8217; after its usage reaches zero, which is a prohibited operation. This oversight can potentially be <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2024-49563-improper-neutralization-exploit-in-dell-unity-leads-to-privilege-escalation\/\"  data-wpil-monitor-id=\"56781\">exploited by malicious actors to compromise the system or lead<\/a> to data leakage.<\/p>\n<p><strong>Conceptual Example Code<\/strong><\/p><div id=\"ameeb-1441929606\" 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 a conceptual example of how the <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-45997-exploiting-file-upload-vulnerability-in-web-based-pharmacy-product-management-system\/\"  data-wpil-monitor-id=\"57517\">vulnerability might be exploited<\/a>:<\/p>\n<pre><code class=\"\" data-line=\"\">struct key *key;\n\/*...*\/\nkey = key_get(some_key);\n\/*...*\/\n\/\/ reduce the reference counter to 0\nfor (int i = 0; i &lt; key-&gt;usage; i++) {\nkey_put(key);\n}\n\/*...*\/\n\/\/ Now, a malicious actor may exploit the use-after-free vulnerability\nmalicious_operation(key);<\/code><\/pre>\n<p>It&#8217;s important to note that this is a simplified, hypothetical example and actual exploitation would require a more complex understanding of the key management subsystem and the <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2024-49841-exploiting-memory-corruption-in-headless-peripheral-vms\/\"  data-wpil-monitor-id=\"58475\">kernel&#8217;s<\/a> memory management.<\/p>\n<p><strong>Impact of Exploit<\/strong><\/p>\n<p>A successful exploit of this <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-5058-arbitrary-file-upload-vulnerability-in-emagicone-store-manager-for-woocommerce-plugin\/\"  data-wpil-monitor-id=\"54665\">vulnerability could allow an attacker to execute arbitrary<\/a> code in the context of the kernel, leading to potential system compromise or data leakage. This could have far-reaching impacts, from <a href=\"https:\/\/www.ameeba.com\/blog\/cve-2025-39350-unauthorized-access-vulnerability-in-rocket-apps-wproject\/\"  data-wpil-monitor-id=\"55640\">unauthorized access<\/a> to sensitive data, to the potential for further system-level exploits.<\/p>\n<p><strong>Recommendations<\/strong><\/p>\n<p>In light of this vulnerability, users are strongly advised to apply the vendor patch as soon as possible. In the event that immediate patching is not feasible, the use of a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can serve as a temporary mitigation measure. However, these should not be seen as long-term solutions and patching should be undertaken as soon as practical.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Overview The Linux kernel, a key component of many global server infrastructures, has been found to contain a critical vulnerability in its key management subsystem. The vulnerability, tracked as CVE-2025-21893, pertains to the &#8216;key_put()&#8217; function, which is responsible for reducing a key&#8217;s reference count. When mishandled, this can lead to the premature destruction of keys [&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-48677","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\/48677","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=48677"}],"version-history":[{"count":9,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/48677\/revisions"}],"predecessor-version":[{"id":66764,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/48677\/revisions\/66764"}],"wp:attachment":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/media?parent=48677"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/categories?post=48677"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/tags?post=48677"},{"taxonomy":"vendor","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/vendor?post=48677"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/product?post=48677"},{"taxonomy":"attack_vector","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/attack_vector?post=48677"},{"taxonomy":"asset_type","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/asset_type?post=48677"},{"taxonomy":"severity","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/severity?post=48677"},{"taxonomy":"exploit_status","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/exploit_status?post=48677"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}