CVE-2013-5600 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the nsIOService::NewChannelFromURIWithProxyFlags function in Mozilla Firefox before 25.0, Firefox ESR 17.x before 17.0.10 and 24.x before 24.1, Thunderbird before 24.1, Thunderbird ESR 17.x before 17.0.10, and SeaMonkey before 2.22 allows remote attackers to execute arbitrary code via vectors involving a blob: URL.
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Analysis
by VulDB Data Team • 11/25/2025
The CVE-2013-5600 vulnerability represents a critical use-after-free flaw in Mozilla's networking subsystem that affected multiple browser and email applications. This vulnerability resides within the nsIOService::NewChannelFromURIWithProxyFlags function, which handles the creation of network channels for various URI schemes including blob: URLs. The flaw occurs when the application processes blob URLs that reference objects in memory that have already been freed, creating a scenario where attackers can manipulate memory contents to execute arbitrary code. The vulnerability is particularly dangerous because it leverages the blob URL mechanism, which is commonly used for handling binary data in web applications and can be easily constructed through JavaScript.
The technical exploitation of this vulnerability involves crafting malicious blob URLs that trigger the use-after-free condition when the browser attempts to process these URLs through the affected function. When a blob URL references freed memory, attackers can manipulate the memory layout to redirect execution flow or inject malicious code. This type of vulnerability is classified as a CWE-416 Use After Free, which is a well-known weakness in memory management where a program continues to use a pointer after the memory it points to has been freed. The flaw is particularly insidious because it allows for remote code execution without requiring user interaction beyond visiting a malicious website or opening a specially crafted email message.
The operational impact of this vulnerability extends across multiple Mozilla products including Firefox, Thunderbird, and SeaMonkey, affecting both regular and extended support release versions. The attack surface is broad since blob URLs are commonly used in web applications for handling file uploads, canvas operations, and other binary data processing. This vulnerability enables attackers to perform privilege escalation attacks, potentially compromising user systems and accessing sensitive data. The exploitability is enhanced by the fact that blob URLs can be generated dynamically through JavaScript, making it difficult for security systems to detect and block malicious activity. According to ATT&CK framework, this vulnerability maps to T1059 Command and Scripting Interpreter and T1068 Exploitation for Privilege Escalation, as it allows for code execution and system compromise.
Mitigation strategies for CVE-2013-5600 primarily involve immediate patching of affected software versions, as the vulnerability was addressed through memory management improvements in the affected applications. Users should ensure they are running patched versions of Firefox, Thunderbird, and SeaMonkey, with the specific version requirements being Firefox 25.0, Thunderbird 24.1, and SeaMonkey 2.22. Additionally, security administrators should implement network monitoring to detect suspicious blob URL patterns and consider browser hardening measures such as disabling unnecessary JavaScript features and restricting blob URL handling. Organizations should also maintain updated threat intelligence feeds to identify potential exploitation attempts targeting this vulnerability, as the use-after-free nature of the flaw makes it attractive for attackers seeking to establish persistent access to compromised systems.