CVE-2015-0803 in Firefox
Summary
by MITRE
The HTMLSourceElement::AfterSetAttr function in Mozilla Firefox before 37.0 does not properly constrain the original data type of a casted value during the setting of a SOURCE element's attributes, which allows remote attackers to execute arbitrary code or cause a denial of service (use-after-free) via a crafted HTML document.
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Analysis
by VulDB Data Team • 05/02/2022
The vulnerability identified as CVE-2015-0803 resides within the HTMLSourceElement::AfterSetAttr function of Mozilla Firefox versions prior to 37.0, representing a critical security flaw that undermines the browser's attribute handling mechanisms. This issue stems from improper type constraint enforcement during the casting of attribute values within SOURCE elements, creating a dangerous condition that can be exploited by malicious actors to gain unauthorized code execution capabilities. The vulnerability specifically affects the browser's rendering engine's ability to properly validate and sanitize data types when processing HTML source elements, which are commonly used in multimedia content delivery through the HTML5 video and audio tags.
The technical flaw manifests as a use-after-free condition that occurs when the browser attempts to cast and set attributes on SOURCE elements without proper validation of the original data type. This improper casting allows attackers to manipulate the memory layout of the browser process by injecting crafted attribute values that, when processed, result in memory corruption. The vulnerability exploits a fundamental weakness in the browser's type system where the AfterSetAttr function fails to enforce strict type checking before performing value casting operations, creating opportunities for attackers to manipulate the execution flow through carefully crafted HTML documents. The issue falls under the CWE-467 weakness category, which specifically addresses the use of sizeof() on pointers rather than arrays, though in this case the root cause involves improper type handling during attribute assignment operations.
The operational impact of this vulnerability extends beyond simple code execution to encompass potential denial of service conditions that can crash the browser or render it unstable. Remote attackers can leverage this flaw by constructing malicious HTML documents containing specially crafted SOURCE element attributes that trigger the vulnerable code path when the browser attempts to render the page. The exploitation process typically involves creating a sequence of attribute assignments that, when processed by the AfterSetAttr function, result in dangling pointers or corrupted memory structures that can be leveraged for arbitrary code execution. This vulnerability directly aligns with ATT&CK technique T1059.007, which covers the use of scripting languages for code execution, and T1499.004, related to the use of system binaries for exploitation purposes.
The remediation strategy for CVE-2015-0803 requires immediate upgrading to Mozilla Firefox version 37.0 or later, which incorporates proper type constraint validation within the HTMLSourceElement::AfterSetAttr function. Security patches implemented in Firefox 37.0 address the root cause by enforcing strict data type validation before any casting operations occur, thereby preventing the exploitation of the use-after-free condition. Organizations should also implement additional defensive measures including web application firewalls, content security policies, and regular security assessments to prevent the delivery of malicious HTML content that could exploit this vulnerability. The fix demonstrates proper input validation and sanitization practices that align with industry standards for secure web browser development and help prevent similar vulnerabilities in other browser implementations.