CVE-2017-8105 in Outside In Technology
Summary
by MITRE
FreeType 2 before 2017-03-24 has an out-of-bounds write caused by a heap-based buffer overflow related to the t1_decoder_parse_charstrings function in psaux/t1decode.c.
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Analysis
by VulDB Data Team • 08/31/2023
The vulnerability identified as CVE-2017-8105 represents a critical heap-based buffer overflow affecting FreeType 2 font rendering library versions prior to the 2017-03-24 release. This issue resides within the Type 1 font decoding functionality and specifically impacts the t1_decoder_parse_charstrings function located in the psaux/t1decode.c source file. The flaw manifests when processing maliciously crafted Type 1 font files that contain malformed character string data, leading to improper memory management during the decoding process.
The technical implementation of this vulnerability stems from inadequate bounds checking within the font parsing routine. When FreeType attempts to decode Type 1 font characters, the t1_decoder_parse_charstrings function processes character string data without sufficient validation of array boundaries. This allows an attacker to provide specially crafted font data that causes the decoder to write beyond the allocated heap memory region. The out-of-bounds write condition occurs because the function does not properly validate the length of character string data against the allocated buffer size, creating a scenario where memory corruption can occur at arbitrary locations within the process heap.
The operational impact of CVE-2017-8105 extends beyond simple memory corruption, as it creates potential vectors for arbitrary code execution within applications that utilize FreeType for font rendering. Since FreeType is widely integrated into numerous operating systems, web browsers, and desktop applications, this vulnerability can be exploited across a broad attack surface. When exploited successfully, the buffer overflow can lead to denial of service conditions, application crashes, or potentially allow remote attackers to execute malicious code with the privileges of the affected application. The vulnerability's severity is amplified by the fact that Type 1 fonts are still commonly used in various environments, including legacy systems and specialized applications that continue to support this font format.
Security researchers have classified this vulnerability according to CWE-121, which describes heap-based buffer overflow conditions where insufficient boundary checks allow writes beyond allocated memory regions. The attack pattern aligns with techniques described in MITRE ATT&CK framework under the T1059.007 sub-technique for command and scripting interpreter, as exploitation could enable attackers to execute arbitrary code through compromised font rendering processes. Organizations should prioritize immediate patching of affected FreeType installations and implement runtime protections such as address space layout randomization and stack canaries to mitigate potential exploitation. Additionally, input validation controls should be strengthened to prevent malformed font data from being processed by applications relying on FreeType libraries.