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Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLXI3NHEtZ3hjZy03M2h4
Improper Input Validation in simple_form
file_method?
in lib/simple_form/form_builder.rb
; a user-supplied string is invoked as a method call
Incorrect Access Control in Impact
For pages that build a form using user input, it is possible for an attacker to manipulate the input and send any method present in the form object. For example:
<%= simple_form_for @user do |f| %>
<%= f.label @user_supplied_string %>
...
<% end %>
The string provided in the variable @user_supplied_string
would be invoked as a method call inside the @user
object (unless the string contains any of the following: password
, time_zone
, country
, email
, phone
and url
).
By manipulation that input, an attacker could do any of the following:
- Code execution (call actions like
#destroy
) - Denial of Service (by executing a computation intensive method)
- Information Disclosure (check the presence of methods, leak user information)
Patches
The problem was fixed in version 5.0
. Although it's a major version, there should be no issues with upgrading for 4.x
. The reason it was released in a major version is that the configuration SimpleForm.file_methods
was deprecated in order to fix the problem.
Workarounds
The issue only happens with pages that build forms based on user-provided input. If your application doesn't do that, you're not affected.
A workaround is to explicitly pass which type you want for an input since the issue lies on Simple Form's automatically discovery of input types. This can be done using the as
option, like the following:
<%= form.input :avatar, as: :file %>
References
[TDB]
For more information
If you have any questions or comments about this advisory:
- Open an issue in https://github.com/plataformatec/simple_form
- Email us at [email protected]
JSON: https://advisories.ecosyste.ms/api/v1/advisories/MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLXI3NHEtZ3hjZy03M2h4
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Critical
Classification: General
Published: over 4 years ago
Updated: 8 months ago
CVSS Score: 9.8
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Identifiers: GHSA-r74q-gxcg-73hx, CVE-2019-16676
References:
- https://github.com/plataformatec/simple_form/security/advisories/GHSA-r74q-gxcg-73hx
- https://nvd.nist.gov/vuln/detail/CVE-2019-16676
- https://github.com/advisories/GHSA-r74q-gxcg-73hx
- https://github.com/plataformatec/simple_form/commits/master
- http://blog.plataformatec.com.br/2019/09/incorrect-access-control-in-simple-form-cve-2019-16676/
- https://github.com/heartcombo/simple_form/commit/8c91bd76a5052ddf3e3ab9fd8333f9aa7b2e2dd6
- https://github.com/rubysec/ruby-advisory-db/blob/master/gems/simple_form/CVE-2019-16676.yml
Blast Radius: 48.3
Affected Packages
rubygems:simple_form
Dependent packages: 436Dependent repositories: 85,278
Downloads: 68,084,778 total
Affected Version Ranges: < 5.0.0
Fixed in: 5.0.0
All affected versions: 0.4.0, 1.0.0, 1.0.1, 1.0.2, 1.0.3, 1.0.4, 1.1.0, 1.1.1, 1.1.2, 1.1.3, 1.2.0, 1.2.1, 1.2.2, 1.3.0, 1.3.1, 1.4.0, 1.4.1, 1.4.2, 1.5.0, 1.5.1, 1.5.2, 2.0.0, 2.0.1, 2.0.2, 2.0.3, 2.0.4, 2.1.0, 2.1.1, 2.1.2, 2.1.3, 3.0.0, 3.0.1, 3.0.2, 3.0.3, 3.0.4, 3.1.0, 3.1.1, 3.2.0, 3.2.1, 3.3.0, 3.3.1, 3.4.0, 3.5.0, 3.5.1, 4.0.0, 4.0.1, 4.1.0
All unaffected versions: 5.0.0, 5.0.1, 5.0.2, 5.0.3, 5.1.0, 5.2.0, 5.3.0