Source: security-advisories@github.com
OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. In versions 3.3.0 through 3.3.6 and 3.4.0 through 3.4.4, a heap-buffer-overflow (OOB read) occurs in the `istream_nonparallel_read` function in `ImfContextInit.cpp` when parsing a malformed EXR file through a memory-mapped `IStream`. A signed integer subtraction produces a negative value that is implicitly converted to `size_t`, resulting in a massive length being passed to `memcpy`. Versions 3.3.7 and 3.4.5 contain a patch.
OpenEXR, a widely used image format library, is vulnerable to a heap-buffer-overflow due to a flaw in how it handles memory-mapped EXR files. This vulnerability allows attackers to craft malicious EXR files that, when processed, can lead to arbitrary code execution or a denial-of-service, potentially compromising systems that use OpenEXR for image processing. Successful exploitation could lead to complete system takeover.
Step 1: Payload Delivery: The attacker crafts a malicious EXR file with a specifically crafted header and data structures designed to trigger the vulnerability.
Step 2: File Processing: A vulnerable application, such as an image viewer, image processing software, or a content creation tool, attempts to open or process the malicious EXR file.
Step 3: Vulnerability Trigger: The istream_nonparallel_read function in ImfContextInit.cpp is called during the parsing of the EXR file.
Step 4: Integer Underflow: A signed integer subtraction within the function results in a negative value.
Step 5: Implicit Conversion: The negative value is implicitly converted to a size_t (unsigned integer), resulting in a large positive number.
Step 6: Buffer Overflow: The large size_t value is used as the size parameter in a memcpy operation, causing it to read beyond the allocated buffer on the heap.
Step 7: Code Execution/DoS: Depending on the attacker's payload, the overflow can lead to arbitrary code execution (e.g., by overwriting function pointers) or a denial-of-service (e.g., by crashing the application).
The vulnerability lies within the istream_nonparallel_read function in ImfContextInit.cpp of the OpenEXR library. A signed integer subtraction results in a negative value. This negative value is then implicitly converted to size_t, leading to a very large value being used as the size parameter in a memcpy operation. This results in a heap-buffer-overflow because memcpy attempts to read beyond the allocated buffer. The root cause is a lack of proper input validation on the size of the data being read from the EXR file, allowing an attacker to control the size parameter and trigger the overflow. The use of memory-mapped IStream further exacerbates the issue, as it allows for direct access to the memory regions, making exploitation more straightforward.
While no specific APT groups are directly linked to this vulnerability at this time, the widespread use of OpenEXR in various industries (film, gaming, etc.) makes it an attractive target. The vulnerability could be incorporated into existing malware toolkits or used in targeted attacks. CISA KEV status: Not Applicable (as of the provided date).
Monitor file system activity for the creation or modification of EXR files, especially those originating from untrusted sources.
Implement network intrusion detection systems (IDS) to identify suspicious network traffic related to EXR file transfers.
Analyze memory dumps of applications that process EXR files for signs of heap corruption or unusual memory access patterns.
Use static analysis tools to scan OpenEXR library versions for the vulnerable code.
Monitor application logs for errors or crashes that occur during EXR file processing.
Upgrade to OpenEXR versions 3.3.7 or 3.4.5 or later, which contain a patch for the vulnerability.
Implement input validation to verify the size and structure of EXR files before processing them.
Restrict the use of OpenEXR to trusted sources only.
Employ a Web Application Firewall (WAF) to filter malicious EXR file uploads.
Implement memory protection mechanisms, such as Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP), to mitigate the impact of potential exploits.
Regularly update all software that utilizes the OpenEXR library.