CVE-2015-8218 in FFmpeg
Summary
by MITRE
The decode_uncompressed function in libavcodec/faxcompr.c in FFmpeg before 2.8.2 does not validate uncompressed runs, which allows remote attackers to cause a denial of service (out-of-bounds array access) or possibly have unspecified other impact via crafted CCITT FAX data.
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Analysis
by VulDB Data Team • 06/27/2022
The vulnerability identified as CVE-2015-8218 represents a critical buffer overflow flaw within the FFmpeg multimedia framework's handling of CCITT FAX compressed data. This issue exists in the decode_uncompressed function located in libavcodec/faxcompr.c and affects FFmpeg versions prior to 2.8.2. The vulnerability stems from insufficient validation of uncompressed runs within the fax compression algorithm implementation, creating a pathway for malicious actors to exploit the system through carefully crafted CCITT FAX data payloads.
The technical exploitation of this vulnerability occurs when FFmpeg processes malformed fax data that contains invalid uncompressed run specifications. The decode_uncompressed function fails to properly validate the length and boundaries of uncompressed data segments, allowing attackers to provide input that exceeds the allocated buffer space. This lack of input sanitization results in out-of-bounds array access patterns that can trigger memory corruption and system instability. The vulnerability operates at the codec level where the software processes compressed data streams, making it particularly dangerous as it can be triggered during normal media playback operations. According to CWE classification, this represents a CWE-129: Improper Validation of Array Index vulnerability, where the system fails to validate array indices before using them in memory operations.
The operational impact of CVE-2015-8218 extends beyond simple denial of service scenarios to potentially enable more sophisticated attacks. Remote attackers can leverage this vulnerability to cause system crashes, application instability, or in some cases, execute arbitrary code depending on the specific memory corruption patterns. The vulnerability is particularly concerning in environments where FFmpeg is used for processing untrusted media content, such as web applications, media servers, or content management systems. Attackers can craft malicious fax data files that when processed by vulnerable FFmpeg implementations will trigger the out-of-bounds memory access, leading to system crashes or potential privilege escalation. The ATT&CK framework categorizes this as a privilege escalation technique through software vulnerabilities, specifically targeting the execution phase where malicious inputs cause unexpected behavior in multimedia processing components.
Mitigation strategies for CVE-2015-8218 primarily involve immediate patching of FFmpeg installations to versions 2.8.2 or later where the vulnerability has been addressed through proper input validation. System administrators should implement strict input validation policies for all multimedia content processing, particularly when handling external or untrusted media files. Additional protective measures include deploying network segmentation to limit exposure, implementing content filtering mechanisms, and establishing monitoring protocols to detect unusual system behavior indicative of exploitation attempts. Organizations should also consider using sandboxed environments for processing potentially malicious media files and maintaining up-to-date vulnerability management procedures to ensure timely patch deployment across all affected systems. The fix implemented in FFmpeg 2.8.2 specifically addresses the missing validation checks in the fax compression decoder, ensuring that uncompressed run specifications are properly bounded before memory operations are performed.