CVE-2018-5118 in Firefox
Summary
by MITRE
The screenshot images displayed in the Activity Stream page displayed when a new tab is opened is created from the meta tags of websites. An issue was discovered where the page could attempt to create these images through "file:" URLs from the local file system. This loading is blocked by the sandbox but could expose local data if combined with another attack that escapes sandbox protections. This vulnerability affects Firefox < 58.
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Analysis
by VulDB Data Team • 07/20/2024
The vulnerability described in CVE-2018-5118 represents a sandbox escape risk within Firefox's Activity Stream feature that operates when users open new tabs. The core issue stems from how Firefox handles screenshot generation for websites displayed in the activity stream interface, which traditionally relies on meta tags from web pages to create visual representations. When processing these meta tags, the browser attempts to construct screenshot images from "file:" URLs that point to the local file system rather than remote web resources. This behavior creates a potential attack vector where malicious actors could manipulate the system to access local files through the seemingly benign screenshot generation process.
The technical flaw specifically involves Firefox's handling of local file system access within its sandboxed environment. While the browser's sandbox mechanism is designed to prevent direct access to local files, the vulnerability occurs during the screenshot generation phase where file URLs are processed. This creates a scenario where an attacker might craft malicious web content that, when processed through the activity stream feature, could bypass sandbox protections. The vulnerability is particularly concerning because it requires an additional attack vector to achieve full sandbox escape, but the combination of local file access with other exploitation techniques could result in significant data exposure.
The operational impact of this vulnerability extends beyond simple information disclosure, as it could enable attackers to access sensitive local files, user documents, system configurations, or other data stored on the victim's machine. Since the vulnerability specifically affects Firefox versions prior to 58, users running older versions remain at risk even when visiting legitimate websites. The attack surface is particularly broad because the activity stream feature is activated automatically when users open new tabs, making it difficult for users to avoid the vulnerability without updating their browser or disabling the feature entirely. This makes the vulnerability particularly dangerous in environments where users cannot immediately update their software.
Security mitigations for this vulnerability primarily involve updating to Firefox version 58 or later, where the issue has been resolved through improved sandboxing controls and stricter validation of file URLs during screenshot generation. Organizations should also implement browser hardening measures that restrict file system access and monitor for unusual network activity that might indicate exploitation attempts. From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1059.007 for script execution and T1071.004 for application layer protocol usage, while CWE-264 indicates the underlying issue of insufficient sandboxing controls. The vulnerability demonstrates the importance of comprehensive sandbox design that accounts for all possible code paths, particularly those involving file system interactions during seemingly benign operations like screenshot generation.