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GHSA-p4x4-rw2p-8j8m
No affected components available
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:
iframemathnoembednoframesnoscriptplaintextscriptstylesvgxmp
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
- GHSA-p4x4-rw2p-8j8m
- CVE-2020-4054
- https://github.com/rgrove/sanitize/releases/tag/v5.2.1
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data. There is a low impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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