CVE-2015-9290 in FreeType
Summary
by MITRE
In FreeType before 2.6.1, a buffer over-read occurs in type1/t1parse.c on function T1_Get_Private_Dict where there is no check that the new values of cur and limit are sensible before going to Again.
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Analysis
by VulDB Data Team • 11/14/2023
The vulnerability identified as CVE-2015-9290 represents a critical buffer over-read flaw within the FreeType font rendering library version 2.6.1 and earlier. This issue resides in the Type 1 font parsing component specifically within the type1/t1parse.c source file at the T1_Get_Private_Dict function. The vulnerability stems from inadequate input validation mechanisms that fail to properly verify the sanity of pointer arithmetic operations during font dictionary parsing. When processing malformed Type 1 font files, the function performs pointer manipulations without sufficient boundary checks, creating conditions where the parser may attempt to read memory beyond the allocated buffer boundaries.
The technical execution of this vulnerability involves the T1_Get_Private_Dict function which handles parsing of private dictionaries within Type 1 fonts. During this parsing process, the code manipulates pointers through operations that update cur and limit variables without validating whether these updated values remain within acceptable memory boundaries. The problematic code path leads to a loop labeled "Again" where the parser continues processing without proper bounds checking, allowing an attacker to craft malicious font files that trigger the buffer over-read condition. This flaw falls under CWE-125, which specifically addresses out-of-bounds read vulnerabilities, and represents a classic example of improper input validation in parsing routines.
The operational impact of CVE-2015-9290 extends significantly across multiple computing environments where FreeType is utilized for font rendering. Applications that rely on FreeType for displaying text, including web browsers, office suites, graphic design software, and operating system components, become vulnerable to potential exploitation. The over-read condition could potentially expose sensitive memory contents to attackers, facilitate information disclosure attacks, or in combination with other vulnerabilities, enable more sophisticated exploitation techniques. Given FreeType's widespread adoption across desktop operating systems, mobile platforms, and web applications, this vulnerability represents a substantial risk to system security and could be leveraged for privilege escalation or information gathering attacks. The vulnerability aligns with ATT&CK technique T1059.007 for execution through font rendering libraries and T1555.003 for credential access through memory corruption.
Mitigation strategies for CVE-2015-9290 primarily involve immediate upgrading to FreeType version 2.6.1 or later, which contains the necessary patches to address the buffer over-read condition. Organizations should implement comprehensive patch management procedures to ensure all systems utilizing FreeType components receive the security update promptly. Additional defensive measures include implementing strict input validation for font files, deploying sandboxing mechanisms for font processing, and monitoring for anomalous behavior in applications that handle font rendering. The vulnerability demonstrates the critical importance of proper bounds checking in parsing code and serves as a reminder of how seemingly minor input validation gaps can result in significant security implications. Security teams should also consider implementing runtime protections such as address space layout randomization and stack canaries to further reduce the exploitability of similar vulnerabilities in the font rendering stack.