- Severity: CRITICAL
- CVE: CVE-2026-122006
- Ecosystems: rubygems, rubygems
- Packages: activestorage, activestorage
### Impact
A Rails application that processes attachments with ImageMagick may allow an unauthenticated attacker to write arbitrary files on the server and, when attachments are stored with the Disk service, to read arbitrary files readable by the application process. Those files typically include `secret_key_base` and credentials for external systems, which may in turn allow escalation to remote code execution or lateral movement to those systems.
### Details
ImageMagick selects a coder from the content of the file it is given, and some coders act on files named inside the image rather than on the image itself. Active Storage constrained none of ImageMagick’s coders, and the ImageMagick analyzer runs when a file is attached, so an attacker who can upload a crafted file may be able to invoke one. Attaching the upload is sufficient; no variant, preview, or `analyze` call is required. One specific attack chain has been reported to us, but we do not assume it is the only one that exists.
The fixed versions ship an ImageMagick security policy and prepend its directory to `MAGICK_CONFIGURE_PATH` through `MiniMagick.cli_env`, so every ImageMagick process that MiniMagick spawns applies it. The policy denies the `MSL` scripting coder, the coders that read or delete files other than the image, fetch remote or local references, or display to a screen, every coder backed by Ghostscript together with the `gs` delegate, and `@filename` indirection. ImageMagick applies every `policy.xml`…
Source: GitHub Security Advisories · 2026-11-12