CVE-2015-3826 in Android
Summary
by MITRE
The MPEG4Extractor::parse3GPPMetaData function in MPEG4Extractor.cpp in libstagefright in Android before 5.1.1 LMY48I does not enforce a minimum size for UTF-16 strings containing a Byte Order Mark (BOM), which allows remote attackers to cause a denial of service (integer underflow, buffer over-read, and mediaserver process crash) via crafted 3GPP metadata, aka internal bug 20923261, a related issue to CVE-2015-3828.
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Analysis
by VulDB Data Team • 06/03/2022
The vulnerability described in CVE-2015-3826 resides within the Android multimedia framework, specifically in the libstagefright library's MPEG4Extractor component. This flaw affects Android versions prior to 5.1.1 LMY48I and represents a critical security issue that can be exploited remotely to cause system instability and denial of service conditions. The vulnerability manifests in the MPEG4Extractor::parse3GPPMetaData function which processes metadata contained within 3GPP multimedia files, a common format used in mobile communications and multimedia applications. The core issue stems from insufficient input validation mechanisms that fail to properly handle UTF-16 encoded strings containing Byte Order Mark (BOM) sequences.
The technical flaw involves a failure to enforce minimum size constraints for UTF-16 strings that include a Byte Order Mark, creating a scenario where maliciously crafted 3GPP files can trigger integer underflow conditions within the parsing logic. When the parser encounters malformed metadata with improperly sized UTF-16 strings, it attempts to perform buffer operations using calculated values that fall below acceptable thresholds, leading to buffer over-read conditions. This vulnerability operates at the intersection of multiple security concerns and can be categorized under CWE-129, which addresses insufficient validation of length of input buffers, and CWE-190, which covers integer overflow/underflow conditions. The flaw demonstrates characteristics consistent with the ATT&CK technique T1203, where adversaries leverage input validation weaknesses to manipulate system memory operations.
The operational impact of this vulnerability extends beyond simple denial of service, as it can completely crash the mediaserver process which is responsible for handling multimedia content processing across the Android platform. When exploited, the vulnerability causes the affected process to terminate unexpectedly, potentially disrupting multimedia applications, media playback functionality, and overall system stability. Attackers can craft malicious 3GPP files that contain specially formatted metadata with invalid UTF-16 string lengths, which when processed by the vulnerable libstagefright component trigger the integer underflow and subsequent buffer over-read conditions. The mediaserver process crash results in a complete loss of multimedia processing capabilities until the system recovers or the user manually restarts the service.
Mitigation strategies for CVE-2015-3826 focus on implementing proper input validation and bounds checking within the affected parsing functions. System administrators should prioritize updating Android devices to version 5.1.1 or later where the vulnerability has been patched through enhanced bounds checking for UTF-16 string processing. The fix typically involves adding explicit minimum size validation for strings containing BOM sequences before any buffer operations are performed. Organizations should also implement network-based filtering to prevent the processing of untrusted multimedia content, particularly when such content originates from external sources or unverified users. Additionally, mobile device management solutions should enforce security policies that prevent automatic processing of multimedia content from unknown or untrusted sources, reducing the attack surface for this particular vulnerability while maintaining system functionality. The patch addresses the root cause by ensuring that all UTF-16 strings undergo proper size validation before any parsing operations occur, thereby preventing the integer underflow conditions that lead to the exploitable buffer over-read scenarios.