CVE-2017-6888 in FLAC
Summary
by MITRE
An error in the "read_metadata_vorbiscomment_()" function (src/libFLAC/stream_decoder.c) in FLAC version 1.3.2 can be exploited to cause a memory leak via a specially crafted FLAC file.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 03/07/2023
The vulnerability identified as CVE-2017-6888 represents a memory management flaw within the Free Lossless Audio Codec implementation specifically affecting version 1.3.2. This issue manifests in the read_metadata_vorbiscomment_() function located within the src/libFLAC/stream_decoder.c source file, where improper handling of metadata structures leads to resource exhaustion through memory allocation without subsequent deallocation. The flaw occurs during the processing of vorbis comment metadata blocks within FLAC audio files, creating a condition where allocated memory segments remain unreleased even after the decoding process completes.
The technical exploitation of this vulnerability relies on crafting a malicious FLAC file containing malformed vorbis comment metadata that triggers the problematic code path within the stream decoder. When the affected library processes such a file, the read_metadata_vorbiscomment_() function allocates memory for metadata parsing but fails to properly release these allocations, resulting in a progressive memory leak that can consume available system resources over time. This memory consumption pattern represents a classic denial of service vector that can be amplified through repeated processing of malicious files or sustained exposure in applications that continuously decode FLAC content.
From an operational perspective, this vulnerability poses significant risks to systems that rely on libFLAC for audio processing, particularly in server environments, media processing pipelines, and applications that handle untrusted audio content. The memory leak can gradually degrade system performance until complete resource exhaustion occurs, potentially leading to application crashes or system instability. Security researchers have categorized this issue under CWE-401, which specifically addresses improper release of memory, making it a direct descendant of memory management deficiencies in software implementations. The vulnerability demonstrates how seemingly benign metadata processing can become a critical security concern when proper resource management protocols are not observed.
The attack surface for this vulnerability extends across numerous applications that utilize the libFLAC library, including media players, audio editing software, streaming services, and content management systems. Attackers can exploit this weakness by preparing specially crafted FLAC files designed to trigger the memory leak condition, potentially causing systems to become unresponsive or crash. Organizations implementing security controls should consider this vulnerability within their threat modeling exercises, particularly for systems processing user-uploaded content or operating in high-volume audio processing environments. The remediation approach involves updating to patched versions of the libFLAC library, typically version 1.3.3 or later, where proper memory cleanup procedures have been implemented to address the resource management issue.
This vulnerability aligns with ATT&CK technique T1499.001, which covers resource exhaustion attacks targeting memory, and demonstrates how memory management flaws can be weaponized for denial of service operations. The flaw serves as a reminder of the critical importance of proper resource management in cryptographic and media processing libraries, where memory leaks can have cascading effects on system stability and availability. System administrators and security teams should prioritize patching this vulnerability as part of their regular maintenance routines, particularly in environments where audio processing occurs with untrusted input sources. The incident underscores the necessity of thorough code review processes for memory management, especially in libraries that handle multimedia content processing where resource exhaustion can be both subtle and impactful.