Helm vulnerable to denial of service through schema file

Fuzz testing, by Ada Logics and sponsored by the CNCF, identified input to functions in the chartutil package that can cause a segmentation violation. Applications that use functions from the chartutil package in the Helm SDK can have a Denial of Service attack when they use this package and it panics.

Impact

The chartutil package contains a parser that loads a JSON Schema validation file. For example, the Helm client when rendering a chart will validate its values with the schema file. The chartutil package parses the schema file and loads it into structures Go can work with. Some schema files can cause array data structures to be created causing a memory violation.

Applications that use the chartutil package in the Helm SDK to parse a schema file can suffer a Denial of Service when that input causes a panic that cannot be recovered from.

The Helm Client will panic with a schema file that causes a memory violation panic. Helm is not a long running service so the panic will not affect future uses of the Helm client.

Patches

This issue has been resolved in 3.10.3.

Workarounds

SDK users can validate schema files that are correctly formatted before passing them to the chartutil functions.

For more information

Helm’s security policy is spelled out in detail in our SECURITY document.

Credits

Disclosed by Ada Logics in a fuzzing audit sponsored by CNCF.