CVE-2018-20760 in GPAC
Summary
by MITRE
In GPAC 0.7.2, gf_text_get_utf8_line in media_tools/text_import.c in libgpac_static.a allows an out-of-bounds write because a certain -1 return value is mishandled.
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Analysis
by VulDB Data Team • 07/06/2023
The vulnerability identified as CVE-2018-20760 represents a critical out-of-bounds write flaw within the GPAC multimedia framework version 0.7.2. This issue resides in the gf_text_get_utf8_line function located in the media_tools/text_import.c file of the libgpac_static.a library, which forms a core component of the GPAC media processing toolkit used extensively in digital content creation and multimedia applications. The flaw manifests when the function encounters a specific return value of -1 from an underlying operation, which is improperly handled leading to memory corruption. This type of vulnerability falls under the CWE-121 category of Stack-based Buffer Overflow, though it more accurately represents a heap-based out-of-bounds write scenario given the nature of the memory management involved in text processing operations. The vulnerability exposes the system to potential arbitrary code execution when maliciously crafted text files are processed through the affected library, as attackers can manipulate the text import functionality to overwrite adjacent memory regions.
The technical implementation of this vulnerability stems from improper error handling within the text parsing routine that processes UTF-8 encoded text data. When the gf_text_get_utf8_line function processes input text, it performs character-by-character analysis to extract lines while maintaining internal buffer pointers and size tracking mechanisms. The mishandling of the -1 return value indicates that the function fails to properly validate the outcome of UTF-8 decoding operations or character boundary calculations. This failure creates a scenario where the function continues execution with invalid buffer parameters, ultimately leading to memory writes beyond the allocated bounds of the target buffer. The operational impact is particularly severe given that GPAC is widely used in multimedia applications, streaming platforms, and content management systems where text import functionality is routinely invoked during media processing workflows. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1059.007 for Command and Scripting Interpreter, as exploitation could enable attackers to inject malicious text data that triggers the vulnerable code path during normal application operation.
The exploitation of this vulnerability requires an attacker to craft malicious text input that triggers the specific code path leading to the out-of-bounds write condition. This typically involves creating specially formatted UTF-8 text files with particular byte sequences that cause the function to return -1, followed by subsequent operations that write beyond buffer boundaries. The vulnerability's impact extends beyond simple memory corruption as it can potentially be leveraged for privilege escalation or remote code execution depending on the execution context of the affected applications. Organizations using GPAC 0.7.2 are particularly vulnerable as this version lacks proper bounds checking and input validation mechanisms that would prevent the propagation of invalid return values into memory operations. The flaw represents a significant security risk in environments where multimedia processing applications handle untrusted text input, such as content management systems, media streaming platforms, and digital asset management solutions. Security practitioners should note that this vulnerability aligns with the broader category of memory safety issues that have been increasingly targeted in recent exploit campaigns, particularly in multimedia and content processing frameworks where complex parsing routines are common. The recommended mitigation involves immediate upgrading to GPAC versions that include proper error handling for return values and enhanced bounds checking mechanisms, while also implementing input validation policies that restrict the processing of untrusted text data through the affected library functions.