CVE-2018-5153 in Firefox
Summary
by MITRE
If websocket data is sent with mixed text and binary in a single message, the binary data can be corrupted. This can result in an out-of-bounds read with the read memory sent to the originating server in response. This vulnerability affects Firefox < 60.
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Analysis
by VulDB Data Team • 02/04/2020
This vulnerability resides in the websocket implementation of firefox browsers versions prior to 60, where improper handling of mixed text and binary data within a single websocket message leads to memory corruption. The flaw occurs when websocket frames contain both text and binary data segments that are processed together, creating a scenario where binary data becomes corrupted during transmission. This corruption manifests as an out-of-bounds read operation that allows malicious data to be read from memory locations and subsequently transmitted back to the originating server. The vulnerability stems from inadequate validation and processing of websocket frame boundaries when mixed content types are present within a single message. According to CWE-129, this represents an implementation flaw in bounds checking mechanisms, while the ATT&CK framework would classify this under technique T1059.007 for command and scripting interpreter with potential for remote code execution through memory corruption.
The operational impact of this vulnerability extends beyond simple data corruption, as the out-of-bounds read can expose sensitive memory contents including session tokens, user credentials, or application data to the remote server. This creates a significant information disclosure risk where attackers can potentially harvest valuable data from the victim's browser memory. The mixed text and binary data processing pathway provides a unique attack vector that exploits the websocket protocol's flexibility in handling different data types within a single communication frame. Attackers can craft malicious websocket messages that trigger this condition, causing the browser to read memory beyond intended boundaries and send this data back to their server. The vulnerability affects not just the local browser but also the server that receives the corrupted data, potentially enabling further attacks through information leakage.
Mitigation strategies for this vulnerability focus on both immediate remediation and architectural improvements. The primary solution involves upgrading to firefox version 60 or later where the websocket implementation has been corrected to properly handle mixed text and binary data within single messages. Organizations should also implement websocket traffic monitoring to detect anomalous data patterns that might indicate exploitation attempts. Network security controls can be configured to inspect websocket frames for malformed mixed content patterns, though this requires deep packet inspection capabilities. The fix implemented in firefox 60 addresses the core issue by strengthening the validation of websocket frame boundaries and ensuring proper handling of data type transitions within frames. Security teams should also consider implementing additional layers of protection such as content security policies and websocket-specific security headers to limit the impact of any potential exploitation attempts. Regular security assessments of websocket implementations and browser configurations remain essential for maintaining defense in depth against similar memory corruption vulnerabilities.