Apache Tomcat: RCE due to TOCTOU issue in JSP compilation - CVE-2024-50379 mitigation was incomplete

Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in Apache Tomcat.

This issue affects Apache Tomcat: from 11.0.0 through 11.0.1, from 10.1.0 through 10.1.33, from 9.0.0 through 9.0.97.
The following versions were EOL at the time the CVE was created but are
known to be affected: 8.5.0 though 8.5.100. Other, older, EOL versions
may also be affected.

The mitigation for CVE-2024-50379 was incomplete.

Users running Tomcat on a case insensitive file system with the default servlet write enabled (readonly initialisation
parameter set to the non-default value of false) may need additional configuration to fully mitigate CVE-2024-50379 depending on which version of Java they are using with Tomcat:

• running on Java 8 or Java 11: the system property sun.io.useCanonCaches must be explicitly set to false (it defaults to true)
• running on Java 17: the system property sun.io.useCanonCaches, if set, must be set to false (it defaults to false)
• running on Java 21 onwards: no further configuration is required (the system property and the problematic cache have been removed)

Tomcat 11.0.3, 10.1.35 and 9.0.99 onwards will include checks that sun.io.useCanonCaches is set appropriately before allowing the default servlet to be write enabled on a case insensitive file system. Tomcat will also set sun.io.useCanonCaches to false by default where it can.