{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/products/mistune-image-directive/feed.json","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[{"cvss":4.7,"id":"CVE-2026-44899"}],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["Mistune Image Directive"],"_cs_severities":["medium"],"_cs_tags":["css-injection","vulnerability","mistune"],"_cs_type":"threat","_cs_vendors":["Microsoft"],"content_html":"\u003cp\u003eCVE-2026-44899 is a CSS Injection vulnerability affecting the Mistune Image Directive. Mistune is a fast, full-featured pure Python Markdown parser. The Image Directive extension allows for the inclusion of images with specific attributes in Markdown documents. This vulnerability could allow an attacker to inject malicious CSS code if user-supplied data is not properly sanitized, potentially leading to cross-site scripting (XSS) or other client-side attacks if the crafted Markdown is rendered in a web browser. This can lead to information disclosure or other malicious activity, depending on the context of the application using Mistune.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAn attacker crafts a malicious Markdown document containing a crafted image directive with CSS injection payloads.\u003c/li\u003e\n\u003cli\u003eThe attacker submits the crafted Markdown document to an application that uses Mistune to render Markdown.\u003c/li\u003e\n\u003cli\u003eThe Mistune parser processes the Markdown document, including the malicious image directive, without proper sanitization.\u003c/li\u003e\n\u003cli\u003eThe injected CSS payload is embedded into the resulting HTML output.\u003c/li\u003e\n\u003cli\u003eA user views the rendered HTML page in a web browser.\u003c/li\u003e\n\u003cli\u003eThe browser executes the injected CSS, potentially leading to XSS if combined with other vulnerabilities or misconfigurations.\u003c/li\u003e\n\u003cli\u003eThe attacker leverages the XSS to steal cookies, redirect the user to a malicious website, or deface the website.\u003c/li\u003e\n\u003cli\u003eThe attacker gains unauthorized access to the user\u0026rsquo;s account or system, or spreads malware.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation of this vulnerability could allow an attacker to inject malicious CSS code, leading to potential cross-site scripting (XSS) attacks. Depending on the application\u0026rsquo;s implementation, this could result in unauthorized access, information disclosure, or defacement of web pages. The number of victims and affected sectors would depend on the popularity and usage of applications employing the vulnerable Mistune Image Directive.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eUpgrade to a patched version of Mistune that addresses CVE-2026-44899, ensuring proper sanitization of user-supplied content in image directives.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rule \u0026ldquo;Detect CSS Injection Attempts via Image Directive\u0026rdquo; to detect attempts to inject malicious CSS code through image directives.\u003c/li\u003e\n\u003cli\u003eImplement robust input validation and output encoding to prevent CSS injection vulnerabilities in applications that use Mistune.\u003c/li\u003e\n\u003cli\u003eRegularly scan applications for vulnerabilities to identify and remediate potential security risks.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2026-05-28T07:28:47Z","date_published":"2026-05-28T07:28:47Z","id":"https://feed.craftedsignal.io/briefs/2026-05-mistune-css-injection/","summary":"CVE-2026-44899 is a CSS Injection vulnerability in the Mistune Image Directive, potentially allowing for malicious CSS injection if user-supplied content is not properly sanitized.","title":"CVE-2026-44899 Mistune Image Directive CSS Injection Vulnerability","url":"https://feed.craftedsignal.io/briefs/2026-05-mistune-css-injection/"}],"language":"en","title":"CraftedSignal Threat Feed — Mistune Image Directive","version":"https://jsonfeed.org/version/1.1"}