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@renovate renovate bot commented Mar 17, 2023

Mend Renovate

This PR contains the following updates:

Package Change Age Adoption Passing Confidence
org.jsoup:jsoup (source) 1.9.1 -> 1.15.3 age adoption passing confidence

GitHub Vulnerability Alerts

CVE-2021-37714

Impact

What kind of vulnerability is it? Who is impacted?
Those using jsoup to parse untrusted HTML or XML may be vulnerable to DOS attacks. If the parser is run on user supplied input, an attacker may supply content that causes the parser to get stuck (loop indefinitely until cancelled), to complete more slowly than usual, or to throw an unexpected exception. This effect may support a denial of service attack.

Patches

Has the problem been patched? What versions should users upgrade to?
Users should upgrade to jsoup 1.14.2

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?
Users may rate limit input parsing. Users should limit the size of inputs based on system resources. Users should implement thread watchdogs to cap and timeout parse runtimes.

CVE-2022-36033

jsoup may incorrectly sanitize HTML including javascript: URL expressions, which could allow cross-site scripting (XSS) attacks when a reader subsequently clicks that link. If the non-default SafeList.preserveRelativeLinks option is enabled, HTML including javascript: URLs that have been crafted with control characters will not be sanitized. If the site that this HTML is published on does not set a Content Security Policy, an XSS attack is then possible.

Impact

Sites that accept input HTML from users and use jsoup to sanitize that HTML, may be vulnerable to cross-site scripting (XSS) attacks, if they have enabled SafeList.preserveRelativeLinks and do not set an appropriate Content Security Policy.

Patches

This issue is patched in jsoup 1.15.3.

Users should upgrade to this version. Additionally, as the unsanitized input may have been persisted, old content should be cleaned again using the updated version.

Workarounds

To remediate this issue without immediately upgrading:

  • disable SafeList.preserveRelativeLinks, which will rewrite input URLs as absolute URLs
  • ensure an appropriate Content Security Policy is defined. (This should be used regardless of upgrading, as a defence-in-depth best practice.)

Background and root cause

jsoup includes a Cleaner component, which is designed to sanitize input HTML against configurable safe-lists of acceptable tags, attributes, and attribute values.

This includes removing potentially malicious attributes such as <a href="javascript:...">, which may enable XSS attacks. It does this by validating URL attributes against allowed URL protocols (e.g. http, https).

However, an attacker may be able to bypass this check by embedding control characters into the href attribute value. This causes the Java URL class, which is used to resolve relative URLs to absolute URLs before checking the URL's protocol, to treat the URL as a relative URL. It is then resolved into an absolute URL with the configured base URI.

For example, java\tscript:... would resolve to https://example.com/java\tscript:....

By default, when using a safe-list that allows a tags, jsoup will rewrite any relative URLs (e.g. /foo/) to an absolute URL (e.g. https://example.com/foo/). Therefore, this attack attempt would be successfully mitigated. However, if the option SafeList.preserveRelativeLinks is enabled (which does not rewrite relative links to absolute), the input is left as-is.

While Java will treat a path like java\tscript: as a relative path, as it does not match the allowed characters of a URL spec, browsers may normalize out the control characters, and subsequently evaluate it as a javascript: spec inline expression. That disparity then leads to an XSS opportunity.

Sites defining a Content Security Policy that does not allow javascript expressions in link URLs will not be impacted, as the policy will prevent the script's execution.

For more information

If you have any questions or comments about this advisory:

Credits

Thanks to Jens Häderer, who reported this issue, and contributed to its resolution.


Configuration

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