{"id":3223,"date":"2026-05-20T09:04:36","date_gmt":"2026-05-20T09:04:36","guid":{"rendered":"https:\/\/blog.ibvl.in\/index.php\/2026\/05\/20\/how-an-image-could-compromise-your-mac-understanding-an-exiftool-vulnerability-cve-2026-3102\/"},"modified":"2026-05-20T09:04:36","modified_gmt":"2026-05-20T09:04:36","slug":"how-an-image-could-compromise-your-mac-understanding-an-exiftool-vulnerability-cve-2026-3102","status":"publish","type":"post","link":"https:\/\/blog.ibvl.in\/index.php\/2026\/05\/20\/how-an-image-could-compromise-your-mac-understanding-an-exiftool-vulnerability-cve-2026-3102\/","title":{"rendered":"How an image could compromise your Mac: understanding an ExifTool vulnerability (CVE-2026-3102)"},"content":{"rendered":"
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\"exiftools<\/p>\n

Introduction<\/h2>\n

ExifTool<\/a> is a widely adopted utility for reading and writing metadata in image, PDF, audio, and video files. It is available both as a standalone command-line application and as a library that can be embedded in other software. In this article, we break down CVE-2026-3102<\/a>, an ExifTool vulnerability discovered by Kaspersky\u2019s Global Research and Analysis Team (GReAT) in February 2026 and patched by the developers within the same month. Affecting macOS systems with ExifTool version 13.49 and earlier, this flaw could let an attacker run arbitrary commands by hiding instructions inside an image file\u2019s metadata.<\/p>\n

This investigation originated from revisiting an n-day vulnerability I first examined years ago: CVE-2021-22204<\/a>. That flaw exploited weak regex-based sanitization before feeding user input into an eval sink. By auditing adjacent input validation routines across ExifTool codebase for similar oversights, I discovered CVE-2026-3102<\/a>. Successful exploitation of CVE-2026-3102 enables an attacker to execute arbitrary shell commands with the privileges of the user invoking ExifTool, potentially leading to full system compromise.<\/p>\n

Technical details<\/h2>\n

Disclaimer<\/h3>\n

Exploiting CVE-2026-3102 requires the -n<\/code> (also known as -printConv<\/code>) flag and outputs machine-readable data without additional processing.<\/p>\n

Tracing the vulnerable sink<\/h3>\n

Taint analysis (aka tainted data analysis) allows for the detection of \u201cdirty\u201d data that reaches dangerous locations without validation. In this context, a \u201csink\u201d is a point or function in a program where data or a parameter marked as \u201ctainted\u201d or originating from an untrusted source (e.g., user input) can affect the program\u2019s behavior. In ExifTool, these functions are eval<\/code> and system<\/code>, both of which are capable of executing system commands. While CVE-2021-22204 exploited an eval function as a sink, this vulnerability (CVE-2026-3102) targets the system function. Knowing the vulnerable sink, we needed to trace how user-controlled data reaches it. Below, we break down the details.<\/p>\n

\"\"<\/a><\/p>\n

Finding an unsanitized date value<\/h3>\n

The screenshot above shows where the system() sink resides within the SetMacOSTags<\/code> function. Tracing backward from system()<\/code>, we identified the $cmd variable as the source of the executed command. This variable is assembled from three inputs: $file<\/code> (properly sanitized), $setTags<\/code> (processed iteratively), and $val<\/code> (user-controlled and, crucially, left unsanitized in the vulnerable branch).<\/p>\n

In ExifTool, a tag is a named metadata field. When parsing an image, the utility extracts date and time values from standard EXIF records or macOS filesystem attributes. To handle file creation dates on macOS, ExifTool relies on the Spotlight system attribute MDItemFSCreationDate<\/code>. Within the program code, this attribute maps to the internal alias $FileCreateDate. These two identifiers govern how the file creation date is stored and applied.<\/p>\n

This creates a critical link to the vulnerability: when parsing an image, ExifTool iterates through the discovered tags. The current tag\u2019s name is assigned to the $tag variable, while its text content (e.g., a date string) is assigned to $val. The vulnerable code path is triggered only when $tag matches MDItemFSCreationDate<\/code> or $FileCreateDate<\/code>. At this point, the tag\u2019s content flows into $val and is passed to the SetMacOSTags function. As shown in the screenshot below, the filename parameter is properly escaped, but the date value ($val<\/code>) is not. Because the date is extracted directly from file metadata, an attacker can inject quotes into this field. This breaks the command structure and allows the payload to execute via the system()<\/code> sink.<\/p>\n

The following screenshots show some of the tags that can be modified. With the vulnerable parameter identified, the next challenge was delivery: how to place our payload into FileCreateDate<\/code> without triggering early validation? We found the answer in the official documentation.<\/p>\n

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Planning the payload delivery<\/h3>\n

Let\u2019s refer to the documentation<\/a> to understand how ExifTool handles tag operations and identify a legitimate feature that can be repurposed for exploitation. Specifically, we need to find a way to deliver our payload into the vulnerable FileCreateDate parameter. When looking for macOS-related tags as well as FileCreateDate, we can find the following information:<\/p>\n