CVE-2007-5137 in TCL TK
Summary
by MITRE
Buffer overflow in the ReadImage function in generic/tkImgGIF.c in Tcl (Tcl/Tk) 8.4.13 through 8.4.15 allows remote attackers to execute arbitrary code via multi-frame interlaced GIF files in which later frames are smaller than the first. NOTE: this issue is due to an incorrect patch for CVE-2007-5378.
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Analysis
by VulDB Data Team • 07/27/2019
The vulnerability identified as CVE-2007-5137 represents a critical buffer overflow condition within the Tcl/Tk toolkit's image handling capabilities, specifically affecting versions 8.4.13 through 8.4.15. This flaw resides in the ReadImage function located within the generic/tkImgGIF.c source file, which processes GIF image files for display within Tcl/Tk applications. The vulnerability manifests when processing multi-frame interlaced GIF files where subsequent frames are smaller than the initial frame, creating a scenario that allows attackers to manipulate memory allocation and execution flow. The root cause of this vulnerability stems from an improper patch implementation for CVE-2007-5378, demonstrating how remediation efforts can inadvertently introduce new security weaknesses. This particular buffer overflow vulnerability operates under the Common Weakness Enumeration classification of CWE-121, which encompasses stack-based buffer overflow conditions that can lead to arbitrary code execution. The technical implementation involves memory corruption during image frame processing where the application fails to properly validate frame dimensions against allocated buffer sizes, creating a scenario where attacker-controlled data can overwrite adjacent memory regions.
The operational impact of this vulnerability extends significantly within environments where Tcl/Tk applications process untrusted image data, particularly in web applications, email clients, or any system that renders GIF images without proper input validation. Attackers can craft malicious GIF files that, when processed by vulnerable Tcl/Tk applications, trigger the buffer overflow condition and subsequently execute arbitrary code with the privileges of the affected application. The exploitation requires the target system to process specifically crafted multi-frame interlaced GIF files where frame dimensions are manipulated to exceed allocated buffer boundaries, allowing for stack corruption and potential code execution. This vulnerability directly maps to the attack pattern described in the MITRE ATT&CK framework under the T1059.007 technique for "Command and Scripting Interpreter: PowerShell" and T1203 for "Exploitation for Client Execution," as it enables remote code execution through client-side image processing vulnerabilities. The security implications are particularly severe in web environments where users may unknowingly trigger the exploitation by viewing maliciously crafted images, making this vulnerability a prime target for drive-by download attacks and web-based exploitation campaigns.
Mitigation strategies for CVE-2007-5137 require immediate application of the official patch released by the Tcl/Tk development team, which properly addresses the buffer overflow condition by implementing correct frame dimension validation and memory allocation checks. Organizations should implement comprehensive input validation measures that reject or sanitize GIF files with inconsistent frame dimensions before processing, particularly focusing on interlaced multi-frame images that exhibit size variations between frames. Network-based defenses can be enhanced through content filtering solutions that block or scan GIF image files for suspicious patterns, though this approach remains less effective than application-level patches. System administrators should conduct thorough vulnerability assessments to identify all instances of affected Tcl/Tk versions within their environments, ensuring that all applications relying on these libraries receive appropriate updates. The remediation process must also include monitoring for any attempts to exploit this vulnerability through web traffic analysis and log review for suspicious image processing activities. Additionally, implementing application sandboxing and privilege separation techniques can limit the potential impact of successful exploitation attempts, while regular security updates and patch management procedures should be enforced to prevent similar issues from arising in the future. This vulnerability serves as a critical reminder of the importance of thorough testing and validation of security patches, as the incorrect patch for CVE-2007-5378 inadvertently introduced the conditions that led to CVE-2007-5137, highlighting the complex interdependencies between security fixes and their potential for introducing new attack vectors.