Active Storage allowed transformation methods potentially unsafe
Active Storage attempts to prevent the use of potentially unsafe image
transformation methods and parameters by default.
The default allowed list contains three methods allow for the circumvention
of the safe defaults which enables potential command injection
vulnerabilities in cases where arbitrary user supplied input is accepted as
valid transformation methods or parameters.
Impact
------
This vulnerability impacts applications that use Active Storage with the image_processing processing gem in addition to mini_magick as the image processor.
Vulnerable code will look something similar to this:
``
<%= image_tag blob.variant(params[:t] => params[:v]) %>
``
Where the transformation method or its arguments are untrusted arbitrary input.
All users running an affected release should either upgrade or use one of the workarounds immediately.
Workarounds
-----------
Consuming user supplied input for image transformation methods or their parameters is unsupported behavior and should be considered dangerous.
Strict validation of user supplied methods and parameters should be performed
as well as having a strong
ImageMagick security
policy deployed.
Credits
-------
Thank you
lio346 for reporting this!
SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Track* at medium and Attend at high mission impact.
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)3 days if the affected system is publicly exposed; 60 days if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it