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Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLXA0eDQtcncycC04ajht
Cross-site Scripting in Sanitize
When HTML is sanitized using Sanitize's "relaxed" config or a custom config that allows certain elements, some content in a <math>
or <svg>
element may not be sanitized correctly even if math
and svg
are not in the allowlist.
You are likely to be vulnerable to this issue if you use Sanitize's relaxed config or a custom config that allows one or more of the following HTML elements:
iframe
math
noembed
noframes
noscript
plaintext
script
style
svg
xmp
Impact
Using carefully crafted input, an attacker may be able to sneak arbitrary HTML through Sanitize, potentially resulting in XSS (cross-site scripting) or other undesired behavior when that HTML is rendered in a browser.
Releases
This problem has been fixed in Sanitize 5.2.1.
Workarounds
If upgrading is not possible, a workaround is to override the default value of Sanitize's :remove_contents
config option with the following value, which ensures that the contents of math
and svg
elements (among others) are removed entirely when those elements are not in the allowlist:
%w[iframe math noembed noframes noscript plaintext script style svg xmp]
For example, if you currently use Sanitize's relaxed config, you can create a custom config object that overrides the default value of :remove_contents
like this:
custom_config = Sanitize::Config.merge(
Sanitize::Config::RELAXED,
:remove_contents => %w[iframe math noembed noframes noscript plaintext script style svg xmp]
)
You would then pass this custom config to Sanitize when sanitizing HTML.
For more information
If you have any questions or comments about this advisory:
- Open an issue in the Sanitize repo.
- See Sanitize's security policy.
Credits
Many thanks to Michal Bentkowski of Securitum for reporting this bug and helping to verify the fix.
References Permalink: https://github.com/advisories/GHSA-p4x4-rw2p-8j8m
JSON: https://advisories.ecosyste.ms/api/v1/advisories/MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLXA0eDQtcncycC04ajht
Source: GitHub Advisory Database
Origin: Unspecified
Severity: High
Classification: General
Published: almost 4 years ago
Updated: 12 months ago
CVSS Score: 7.3
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Identifiers: GHSA-p4x4-rw2p-8j8m, CVE-2020-4054
References:
- https://github.com/rgrove/sanitize/security/advisories/GHSA-p4x4-rw2p-8j8m
- https://github.com/rgrove/sanitize/commit/a11498de9e283cd457b35ee252983662f7452aa9
- https://github.com/rgrove/sanitize/releases/tag/v5.2.1
- https://nvd.nist.gov/vuln/detail/CVE-2020-4054
- https://www.debian.org/security/2020/dsa-4730
- https://usn.ubuntu.com/4543-1/
- https://github.com/rubysec/ruby-advisory-db/blob/master/gems/sanitize/CVE-2020-4054.yml
- https://github.com/advisories/GHSA-p4x4-rw2p-8j8m
Blast Radius: 29.4
Affected Packages
rubygems:sanitize
Dependent packages: 258Dependent repositories: 10,715
Downloads: 82,214,987 total
Affected Version Ranges: >= 3.0.0, < 5.2.1
Fixed in: 5.2.1
All affected versions: 3.0.0, 3.0.1, 3.0.2, 3.0.3, 3.0.4, 3.1.0, 3.1.1, 3.1.2, 4.0.0, 4.0.1, 4.1.0, 4.2.0, 4.3.0, 4.4.0, 4.5.0, 4.6.0, 4.6.1, 4.6.2, 4.6.3, 4.6.4, 4.6.5, 4.6.6, 5.0.0, 5.1.0, 5.2.0
All unaffected versions: 1.0.0, 1.0.1, 1.0.2, 1.0.3, 1.0.4, 1.0.5, 1.0.6, 1.0.7, 1.0.8, 1.1.0, 1.2.0, 1.2.1, 2.0.0, 2.0.1, 2.0.2, 2.0.3, 2.0.4, 2.0.5, 2.0.6, 2.1.0, 2.1.1, 5.2.1, 5.2.2, 5.2.3, 6.0.0, 6.0.1, 6.0.2, 6.1.0