CVE-2026-109273 in ImageMagick
Summary
by MITRE • 10/12/2026
ImageMagick before 6.9.13-57 and 7.x before 7.1.2-32 contains an information disclosure vulnerability in the PostScript decoder, which allocates a buffer one byte longer than the data it decoded. Attackers can supply a crafted PostScript file to expose a single uninitialized byte of memory contents.
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Analysis
by VulDB Data Team • 10/12/2026
The identified security flaw resides within the PostScript decoding module of ImageMagick versions prior to 6.9.13-57 and 7.x prior to 7.1.2-32, representing a classic off-by-one error that leads to an out-of-bounds read condition. This vulnerability stems from a miscalculation in the buffer allocation logic during the processing of PostScript input streams. Specifically, when decoding certain PostScript constructs, the software allocates a memory buffer with a size one byte greater than the actual length of the decoded data payload. While this might initially appear to be a benign over-allocation that provides padding for safety, it inadvertently creates an opportunity for information disclosure by leaving the final byte of the allocated heap or stack space uninitialized and accessible during subsequent operations.
From a technical perspective, the core issue is classified under CWE-125, which denotes Out-of-bounds Read. When ImageMagick processes a maliciously crafted PostScript file designed to trigger this specific code path, it reads from the buffer including that extra byte. Because memory allocators do not always zero out newly allocated memory for performance reasons, or because the padding byte was never explicitly initialized by the application logic, this final byte contains residual data from previous allocations or system operations. Consequently, an attacker who can induce ImageMagick to process a specific crafted file can cause the application to expose this single uninitialized byte of memory contents back through the output stream or error messages generated during processing.
The operational impact of this vulnerability is primarily centered on information disclosure rather than direct code execution or denial of service in its basic form. By repeatedly triggering this condition, an attacker may be able to leak sensitive data such as stack canaries, pointers to other memory regions, or parts of the application's internal state that were previously stored at those addresses. This leakage can serve as a critical stepping stone for more advanced attacks. For instance, leaking pointer values allows attackers to bypass Address Space Layout Randomization (ASLR), a fundamental security mechanism in modern operating systems. Once ASLR is defeated, the attacker gains precise knowledge of memory layout, significantly increasing the likelihood of successfully exploiting secondary vulnerabilities such as buffer overflows or use-after-free conditions for arbitrary code execution.
In terms of threat modeling and adversary behavior, this vulnerability aligns with ATT&CK technique T1083, which covers File and Directory Discovery, although in a broader sense it fits into reconnaissance phases where attackers gather information about the target environment to plan further exploitation. It also relates to T1567, Exfiltration Over Web Services, if the leaked data is transmitted out of band via HTTP or other network protocols facilitated by the ImageMagick processing pipeline. The vulnerability highlights the risks associated with image processing libraries that handle untrusted input formats like PostScript, which are historically complex and prone to parsing errors due to their Turing-complete nature in some interpretations.
Mitigation strategies for this issue involve immediate patching of the affected ImageMagick installations to version 6.9.13-57 or later, or version 7.1.2-32 and above, where the buffer allocation logic has been corrected to strictly match the decoded data size without leaving uninitialized bytes accessible. Organizations relying on this library should audit their deployment environments for these specific versions. Additionally, implementing strict input validation and sanitization policies can help mitigate risks from similar parsing vulnerabilities in other components. Deploying Web Application Firewalls (WAFs) with rulesets capable of detecting anomalous PostScript payloads may provide a layer of defense-in-depth against exploitation attempts while patches are being applied. Regular security assessments and code reviews focusing on memory management practices, particularly around buffer sizing and initialization, are essential to prevent recurrence of such off-by-one errors in software development lifecycles.