Description

ImageMagick versions before 7.1.2-32 and 6.9.13-57 contain uninitialized heap memory disclosure in the GIF decoder's application extension handler in coders/gif.c. Attackers can craft malicious GIF files that cause the number parser to read uninitialized heap memory and store contents as image metadata, disclosing sensitive heap information.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "3.7",
  "pubDate": "2026-09-29T17:17:07.323Z",
  "pubdate": "2026-09-29T17:17:07.323Z",
  "executiveSummary": "This vulnerability involves an uninitialized heap memory disclosure located within the ImageMagick GIF decoder's application extension handler.\nThe flaw allows an attacker to craft a malicious GIF file that, when processed, forces the image parser to read and embed uninitialized heap memory contents directly into the image's metadata.\nThe affected versions include ImageMagick prior to 7.1.2-32 and 6.9.13-57.\nThe primary impact is the unauthorized disclosure of sensitive heap information, which may include fragments of processed data, pointers, or security-sensitive structures residing in memory.\nExploitation requires that an attacker successfully cause a target system to process a specially crafted GIF file. No specific authentication or high-level privilege requirements are natively described, though the attack is contingent upon the application's ability to process untrusted user-supplied input.\nSuccessful exploitation potentially enables an attacker to leak heap layouts, facilitating bypasses for security protections like ASLR, or recovering sensitive data processed by the application during its execution cycle.",
  "technicalDetails": "The root cause of this vulnerability lies in the improper handling of data segments within the application extension block of a GIF file, specifically within the coders/gif.c component of ImageMagick.\nDuring the parsing process of the GIF format, the decoder encounters application extension labels. The vulnerability manifests when the internal number parser processes these blocks without ensuring that the underlying memory buffer—destined for storage in image metadata—has been correctly initialized.\nWhen the decoder reads from an uninitialized heap allocation, it effectively snapshots the 'dirty' or residual memory contents currently residing at that memory address. Because this uninitialized memory is then written into the image object's metadata properties, these fragments of private process heap memory become externally accessible via the resulting image file.\nThe attack flow follows a sequential pattern: 1) The attacker constructs a malicious GIF image with malformed or specifically crafted application extension fields designed to trigger the parser's logic error. 2) The target application invokes the ImageMagick decoder to handle the file. 3) The coders/gif.c logic misinterprets the memory allocation state for the metadata field. 4) The parser copies the contents of uninitialized heap memory into the metadata field of the image object. 5) The resulting output image, which is then exposed to the attacker or stored in a way accessible to them, contains the sensitive heap dump.\nThe vulnerability affects versions prior to 7.1.2-32 (ImageMagick 7 series) and 6.9.13-57 (ImageMagick 6 series). There are no stated authentication requirements, making it a low-complexity attack for services that automatically process user-provided imagery.\nPost-exploitation, the disclosed heap data can contain critical information depending on what the application has processed previously. This includes, but is not limited to, private keys, authentication tokens, session IDs, or pointers that reveal the memory layout of the host process. The leakage of memory pointers is particularly concerning as it assists in the development of further exploits, such as Return-Oriented Programming (ROP) chains or memory corruption exploits that rely on predictable memory addresses, effectively neutralizing ASLR protections."
}