{"id":87003,"date":"2026-04-27T04:11:23","date_gmt":"2026-04-27T04:11:23","guid":{"rendered":""},"modified":"-0001-11-30T00:00:00","modified_gmt":"-0001-11-30T06:00:00","slug":"cve-2025-55780-null-pointer-dereference-vulnerability-in-mupdf","status":"publish","type":"post","link":"https:\/\/www.ameeba.com\/blog\/cve-2025-55780-null-pointer-dereference-vulnerability-in-mupdf\/","title":{"rendered":"<strong>CVE-2025-55780: Null Pointer Dereference Vulnerability in MuPDF<\/strong>"},"content":{"rendered":"<p><strong>Overview<\/strong><\/p>\n<p>CVE-2025-55780 is a significant vulnerability found in MuPDF 1.26.4, a popular software tool for rendering EPUB documents. This vulnerability can lead to a system crash, potentially compromising the system or leading to data leakage. Due to the widespread use of this software, this vulnerability presents a severe threat to numerous organizations and individuals worldwide.<\/p>\n<p><strong>Vulnerability Summary<\/strong><\/p>\n<p>CVE ID: CVE-2025-55780<br \/>\nSeverity: High (7.5\/10)<br \/>\nAttack Vector: Remote<br \/>\nPrivileges Required: None<br \/>\nUser Interaction: Required<br \/>\nImpact: System crash, potential system compromise, and data leakage<\/p>\n<p><strong>Affected Products<\/strong><\/p><div id=\"ameeb-4068908955\" 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>MuPDF | 1.26.4<\/p>\n<p><strong>How the Exploit Works<\/strong><\/p>\n<p>The exploit occurs when MuPDF attempts to render a malformed EPUB document. During this process, a null pointer dereference occurs in the function break_word_for_overflow_wrap(). The function calls fz_html_split_flow() to split a FLOW_WORD node, but does not check if node->next is valid before accessing node->next->overflow_wrap. If the split fails or returns a partial node chain, it results in a system crash.<\/p>\n<p><strong>Conceptual Example Code<\/strong><\/p><div id=\"ameeb-43902861\" 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>Here is a conceptual example of how the vulnerability can be exploited using a malformed EPUB file:<\/p>\n<pre><code class=\"\" data-line=\"\">&lt;!DOCTYPE html&gt;\n&lt;html&gt;\n&lt;head&gt;\n&lt;title&gt;Malformed EPUB&lt;\/title&gt;\n&lt;\/head&gt;\n&lt;body&gt;\n&lt;p&gt;\n&lt;!-- Insert malformed FLOW_WORD node here --&gt;\n&lt;span style=&quot;overflow-wrap: break-word;&quot;&gt;...&lt;\/span&gt;\n&lt;\/p&gt;\n&lt;\/body&gt;\n&lt;\/html&gt;<\/code><\/pre>\n<p>In the above example, the &#8216;&#8230;&#8217; can be replaced with a specifically crafted string that triggers the null pointer dereference vulnerability when MuPDF attempts to split the FLOW_WORD node.<\/p>\n<p><strong>Mitigation Guidance<\/strong><\/p>\n<p>Users of MuPDF 1.26.4 are advised to apply the vendor&#8217;s patch to fix this vulnerability. Alternatively, a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can be used as temporary mitigation.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Overview CVE-2025-55780 is a significant vulnerability found in MuPDF 1.26.4, a popular software tool for rendering EPUB documents. This vulnerability can lead to a system crash, potentially compromising the system or leading to data leakage. Due to the widespread use of this software, this vulnerability presents a severe threat to numerous organizations and individuals worldwide. [&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":[],"tags":[],"vendor":[],"product":[],"attack_vector":[],"asset_type":[],"severity":[],"exploit_status":[],"class_list":["post-87003","post","type-post","status-publish","format-standard","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/87003","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=87003"}],"version-history":[{"count":0,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/posts\/87003\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/media?parent=87003"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/categories?post=87003"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/tags?post=87003"},{"taxonomy":"vendor","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/vendor?post=87003"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/product?post=87003"},{"taxonomy":"attack_vector","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/attack_vector?post=87003"},{"taxonomy":"asset_type","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/asset_type?post=87003"},{"taxonomy":"severity","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/severity?post=87003"},{"taxonomy":"exploit_status","embeddable":true,"href":"https:\/\/www.ameeba.com\/blog\/wp-json\/wp\/v2\/exploit_status?post=87003"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}