CVE-2017-5382 in Firefox
Summary
by MITRE
Feed preview for RSS feeds can be used to capture errors and exceptions generated by privileged content, allowing for the exposure of internal information not meant to be seen by web content. This vulnerability affects Firefox < 51.
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Analysis
by VulDB Data Team • 08/02/2020
The vulnerability described in CVE-2017-5382 represents a critical information disclosure flaw within the Firefox web browser that specifically impacts versions prior to 51. This issue manifests through the feed preview functionality designed to allow users to view RSS feed content without fully loading it in the main browser window. The vulnerability stems from insufficient input validation and error handling mechanisms within the feed preview component that processes RSS feed data from potentially malicious sources.
The technical flaw occurs when Firefox processes RSS feed content through its feed preview feature, which creates a separate rendering context for displaying feed items while maintaining access to privileged system resources. When malicious RSS feeds contain specially crafted error conditions or malformed content, the feed preview mechanism fails to properly sanitize these inputs, allowing error messages and exception details to leak into the preview area. These error messages often contain sensitive internal information such as file paths, system configurations, memory addresses, or other privileged data that should remain hidden from regular web content. This behavior directly violates the principle of least privilege and exposes internal system information that could aid attackers in subsequent exploitation attempts.
The operational impact of this vulnerability extends beyond simple information disclosure, as the leaked information can provide attackers with valuable insights for crafting more sophisticated attacks against the target system. The exposure of internal system details such as file system locations, application paths, or memory structures significantly reduces the attack surface and can facilitate advanced exploitation techniques. This vulnerability aligns with CWE-200, which addresses "Information Exposure" and specifically covers cases where error messages reveal sensitive system information. The flaw also maps to ATT&CK technique T1059.007, "Command and Scripting Interpreter: JavaScript,' as attackers could potentially leverage the exposed information to craft more effective JavaScript-based attacks against the browser environment.
Security researchers have documented how this vulnerability can be exploited in practice by crafting malicious RSS feeds that trigger specific error conditions within Firefox's feed preview system. The attack requires minimal user interaction beyond visiting a webpage that loads the malicious feed, making it particularly dangerous in phishing scenarios or when users browse untrusted content. The vulnerability affects not just the feed preview functionality but also demonstrates broader issues with Firefox's content isolation mechanisms and error handling procedures. Organizations using affected Firefox versions should immediately implement mitigations including browser updates, content filtering solutions, and enhanced monitoring of feed preview usage patterns. The remediation process should also include security awareness training for users to recognize potentially malicious content sources and proper feed management practices to prevent automatic feed loading from untrusted origins.