CVE-2024-23635: AntiSamy malicious input can provoke XSS when preserving comments
Impact
There is a potential for a mutation XSS (mXSS) vulnerability in AntiSamy caused by flawed parsing of the HTML being sanitized. To be subject to this vulnerability the preserveComments directive must be enabled in your policy file. As a result, certain crafty inputs can result in elements in comment tags being interpreted as executable when using AntiSamy's sanitized output.
Patches
Patched in AntiSamy 1.7.5 and later. This is due to parsing behavior in the neko-htmlunit dependency, just by updating to a newer version the issue was solved. See important remediation details in the reference given below.
Workarounds
If you cannot upgrade to a fixed version of the library, the following mitigation can be applied until you can upgrade: Manually edit your AntiSamy policy file (e.g., antisamy.xml) by deleting the preserveComments directive or setting its value to false, if present.
As the previously mentioned policy settings are preconditions for the mXSS attack to work, changing them as recommended should be sufficient to protect you against this vulnerability when using a vulnerable version of this library. However, the existing bug would still be present in the parser dependency (neko-htmlunit) and therefore in AntiSamy. The safety of this workaround relies on configurations that may change in the future and don't address the root cause of the vulnerability. As such, it is strongly recommended to upgrade to a fixed version of AntiSamy.
For more information
If you have any questions or comments about this advisory:
Email one of the project co-leaders, listed on the OWASP AntiSamy project page, under "Leaders".
Other sources
AntiSamy is a library for performing fast, configurable cleansing of HTML coming from untrusted sources. Prior to 1.7.5, there is a potential for a mutation XSS (mXSS) vulnerability in AntiSamy caused by flawed parsing of the HTML being sanitized. To be subject to this vulnerability the preserveComments directive must be enabled in your policy file. As a result, certain crafty inputs can result in elements in comment tags being interpreted as executable when using AntiSamy's sanitized output. Patched in AntiSamy 1.7.5 and later.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
maven/org.owasp.antisamy:antisamyto a version that resolves this vulnerability.Fixed in 1.7.5 - Upgrade
Upgrade
AntiSamyto a version that resolves this vulnerability.Fixed in 1.7.5 - Configuration
If you cannot upgrade, manually edit your AntiSamy policy file (e.g., antisamy.xml) and delete the `preserveComments` directive or set its value to `false` (mitigation until upgrading).
AntiSamy policy file (e.g., antisamy.xml) preserveComments = false
Event History
Frequently Asked Questions
What is the severity of CVE-2024-23635?
CVE-2024-23635 is classified as a medium severity vulnerability due to its potential for exploitation through mutation XSS.
How do I fix CVE-2024-23635?
To fix CVE-2024-23635, you should upgrade to AntiSamy version 1.7.5 or later.
What systems are affected by CVE-2024-23635?
CVE-2024-23635 affects versions of AntiSamy up to 1.7.4 when the 'preserveComments' directive is enabled in the policy file.
What type of vulnerability is CVE-2024-23635?
CVE-2024-23635 is a mutation XSS (mXSS) vulnerability caused by improper parsing of sanitized HTML.
Is CVE-2024-23635 easy to exploit?
Exploitation of CVE-2024-23635 requires specific crafty input and the 'preserveComments' directive to be enabled, making it moderately challenging.