{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/tags/cve-2026-4691/feed.json","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["Firefox","Firefox ESR","Thunderbird"],"_cs_severities":["critical"],"_cs_tags":["cve-2026-4691","use-after-free","firefox","thunderbird"],"_cs_type":"advisory","_cs_vendors":["Mozilla"],"content_html":"\u003cp\u003eCVE-2026-4691 describes a critical use-after-free vulnerability within the CSS Parsing and Computation component of Mozilla Firefox, Firefox ESR, and Thunderbird. This flaw can be exploited if a crafted CSS stylesheet is processed by a vulnerable application. The specific versions affected are Firefox before version 149, Firefox ESR before versions 115.34 and 140.9, and Thunderbird before versions 149 and 140.9. A successful exploit could lead to arbitrary code execution in the context of the user running the application. This vulnerability requires immediate attention from organizations utilizing these products.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAn attacker crafts a malicious CSS stylesheet designed to trigger the use-after-free condition.\u003c/li\u003e\n\u003cli\u003eThe attacker hosts the malicious CSS stylesheet on a web server or embeds it within a malicious HTML page.\u003c/li\u003e\n\u003cli\u003eA user opens a web page or email containing the malicious CSS, or otherwise loads the malicious stylesheet in a vulnerable application (Firefox/Thunderbird).\u003c/li\u003e\n\u003cli\u003eThe vulnerable application (Firefox/Thunderbird) parses the malicious CSS stylesheet.\u003c/li\u003e\n\u003cli\u003eThe CSS Parsing and Computation component attempts to access a memory location that has already been freed, triggering the use-after-free condition.\u003c/li\u003e\n\u003cli\u003eThe attacker leverages the use-after-free condition to potentially corrupt memory.\u003c/li\u003e\n\u003cli\u003eThe attacker gains control of program execution.\u003c/li\u003e\n\u003cli\u003eThe attacker executes arbitrary code on the victim's machine.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation of CVE-2026-4691 can lead to arbitrary code execution on the victim's machine. This could allow an attacker to install malware, steal sensitive information, or take control of the affected system. Given the widespread use of Firefox and Thunderbird, a successful exploit could have a significant impact on a large number of users. The severity is rated as critical with a CVSS score of 9.8, indicating a high risk of exploitation.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eImmediately upgrade Firefox to version 149 or later.\u003c/li\u003e\n\u003cli\u003eImmediately upgrade Firefox ESR to version 115.34, 140.9 or later.\u003c/li\u003e\n\u003cli\u003eImmediately upgrade Thunderbird to version 149 or later.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rule \u0026quot;Detect_CVE_2026_4691_Process_Crash\u0026quot; to identify potential exploitation attempts based on application crashes.\u003c/li\u003e\n\u003cli\u003eMonitor web server logs for requests to unusual CSS files or patterns indicative of exploitation attempts.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-02T10:00:00Z","date_published":"2024-01-02T10:00:00Z","id":"https://feed.craftedsignal.io/briefs/2024-01-cve-2026-4691/","summary":"A use-after-free vulnerability (CVE-2026-4691) in the CSS Parsing and Computation component affects Firefox versions prior to 149, Firefox ESR versions prior to 115.34 and 140.9, and Thunderbird versions prior to 149 and 140.9, potentially leading to arbitrary code execution.","title":"Use-After-Free Vulnerability in Firefox, ESR, and Thunderbird CSS Parsing (CVE-2026-4691)","url":"https://feed.craftedsignal.io/briefs/2024-01-cve-2026-4691/"}],"language":"en","title":"CraftedSignal Threat Feed - Cve-2026-4691","version":"https://jsonfeed.org/version/1.1"}