Summary
jsoup may not sanitize code injection XSS attempts if SafeList.preserveRelativeLinks is enabled
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.
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:
- Open an issue in jsoup
- Email the author of jsoup at [email protected]
Credits
Thanks to Jens Häderer, who reported this issue, and contributed to its resolution.
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.
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
CVE-2022-36033 has a CVSS score of 6.1 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.15.3); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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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.
Frequently Asked Questions
- What is CVE-2022-36033? CVE-2022-36033 is a medium-severity cross-site scripting (XSS) vulnerability in org.jsoup:jsoup (maven), affecting versions < 1.15.3. It is fixed in 1.15.3. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- How severe is CVE-2022-36033? CVE-2022-36033 has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of org.jsoup:jsoup are affected by CVE-2022-36033? org.jsoup:jsoup (maven) versions < 1.15.3 is affected.
- Is there a fix for CVE-2022-36033? Yes. CVE-2022-36033 is fixed in 1.15.3. Upgrade to this version or later.
- Is CVE-2022-36033 exploitable, and should I be worried? Whether CVE-2022-36033 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2022-36033 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2022-36033? Upgrade
org.jsoup:jsoupto 1.15.3 or later.