CVE-2025-3839 in Epiphany
Summary
by MITRE • 01/23/2026
A flaw was found in Epiphany, a tool that allows websites to open external URL handler applications with minimal user interaction. This design can be misused to exploit vulnerabilities within those handlers, making them appear remotely exploitable. The browser fails to properly warn or gate this action, resulting in potential code execution on the client device via trusted UI behavior.
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Analysis
by VulDB Data Team • 01/25/2026
The vulnerability identified as CVE-2025-3839 resides within the Epiphany web browser, specifically targeting its handling of external URL handler applications. This flaw represents a sophisticated attack vector that exploits the browser's trust-based interaction model with external applications, creating a pathway for remote code execution through seemingly benign user interactions. The vulnerability stems from the browser's insufficient validation and warning mechanisms when initiating external application launches, allowing malicious websites to leverage this functionality for unauthorized system access.
This technical weakness operates through a combination of UI deception and application handler exploitation, where the browser's interface presents external application launches as trusted operations without adequate user awareness of the potential risks involved. The flaw essentially creates a trust boundary violation where legitimate browser behavior becomes a conduit for malicious activity. When users encounter web content that triggers external application launches, the browser's current implementation fails to provide appropriate security warnings or user consent mechanisms, enabling attackers to manipulate this trusted behavior for exploitation purposes.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass full system compromise through remote code execution capabilities. Attackers can craft malicious web pages that, when visited by unsuspecting users, automatically trigger launches of vulnerable external applications through the browser's URL handler system. This creates a scenario where the browser's trusted UI elements become attack vectors, as users perceive the application launches as legitimate actions while unknowingly executing malicious code on their systems. The vulnerability is particularly dangerous because it leverages user trust in the browser's interface design and normal web browsing behavior.
Security professionals should note this vulnerability's alignment with CWE-693, which addresses protection mechanism failures in security systems, and its relationship to ATT&CK technique T1059.007 for command and scripting interpreter. The flaw represents a classic example of a user interface-based attack vector where the exploitation relies on social engineering through trusted interface elements rather than direct system vulnerabilities. Organizations should implement immediate mitigations including browser updates, application handler restrictions, and user education about the risks of external application launches. Additionally, network-level controls such as content filtering and application whitelisting can help prevent exploitation attempts, while regular security audits should verify proper implementation of external handler security controls to prevent similar vulnerabilities from emerging in other browser implementations.