CVE-2020-25667 in ImageMagick
Summary
by MITRE • 12/09/2020
TIFFGetProfiles() in /coders/tiff.c calls strstr() which causes a large out-of-bounds read when it searches for `"dc:format=\"image/dng\"` within `profile` due to improper string handling, when a crafted input file is provided to ImageMagick. The patch uses a StringInfo type instead of a raw C string to remedy this. This could cause an impact to availability of the application. This flaw affects ImageMagick versions prior to 7.0.9-0.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 12/14/2020
The vulnerability identified as CVE-2020-25667 represents a critical out-of-bounds read flaw within ImageMagick's TIFF image processing functionality. This issue manifests in the TIFFGetProfiles() function located in the coders/tiff.c source file where the application employs the strstr() string searching function to locate the specific pattern "dc:format=\"image/dng\"" within a profile buffer. The flaw occurs when ImageMagick processes maliciously crafted TIFF files that contain improperly formatted metadata, causing the strstr() function to read beyond the allocated memory boundaries of the profile buffer. This improper string handling vulnerability stems from the application's failure to validate buffer limits before performing string operations, creating a scenario where arbitrary memory contents can be accessed and potentially exposed. The vulnerability is classified under CWE-125 as an out-of-bounds read, which represents a fundamental memory safety issue that can lead to information disclosure or application instability. The flaw specifically affects ImageMagick versions prior to 7.0.9-0, indicating that this was a known issue that required a specific patch to address the root cause.
The operational impact of this vulnerability extends beyond simple memory access violations to potentially compromise the availability and stability of applications relying on ImageMagick for image processing. When a maliciously crafted TIFF file is processed, the out-of-bounds read can cause the application to crash or behave unpredictably, leading to denial of service conditions that affect system availability. The vulnerability demonstrates a classic buffer over-read scenario where the strstr() function continues searching beyond the intended buffer boundaries, potentially accessing uninitialized memory or memory belonging to other processes. This type of flaw can be particularly dangerous in web applications or services that process user-uploaded images, as it provides an attack vector for remote code execution or information disclosure attacks. The security implications align with ATT&CK technique T1203 - Exploitation for Client Execution, where adversaries can leverage such memory corruption vulnerabilities to gain unauthorized access to systems. The flaw's impact on availability is significant because it can cause applications to terminate unexpectedly, requiring system administrators to restart services and potentially leading to extended downtime.
The remediation for this vulnerability involved a fundamental architectural change in how string operations are handled within the ImageMagick codebase. The patch implementation replaced raw C string handling with the StringInfo type, which provides better memory management and bounds checking capabilities. This approach addresses the root cause by ensuring that string operations are performed within properly allocated and validated memory boundaries. The StringInfo type provides built-in mechanisms for tracking string length and preventing buffer overflows, effectively eliminating the conditions that allowed the out-of-bounds read to occur. This change represents a security-by-design principle where the application's internal data structures are enhanced to prevent the type of memory corruption that led to the vulnerability. The fix demonstrates the importance of using higher-level abstractions that provide automatic bounds checking rather than relying on low-level string functions that require manual memory management. This patch approach aligns with industry best practices for secure coding and represents a proactive defense against similar vulnerabilities in the future. The implementation of StringInfo type handling ensures that subsequent string operations within the TIFF processing pipeline maintain proper memory boundaries and prevent similar out-of-bounds access patterns from occurring.