Helm Vulnerable to denial of service through string value parsing

Fuzz testing, by Ada Logics and sponsored by the CNCF, identified input to functions in the _strvals_ package that can cause an out of memory panic. Out of memory panics cannot be recovered from. Applications that use functions from the _strvals_ package in the Helm SDK can have a Denial of Service attack when they use this package and it panics.

Impact

The _strvals_ package contains a parser that turns strings into Go structures. For example, the Helm client has command line flags like --set, --set-string, and others that enable the user to pass in strings that are merged into the values. The _strvals_ package converts these strings into structures Go can work with. Some string inputs can cause array data structures to be created causing an out of memory panic.

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

The Helm Client will panic with input to --set, --set-string, and other value setting flags that causes an out of memory 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 3.9.4.

Workarounds

SDK users can validate strings supplied by users won’t create large arrays causing significant memory usage before passing them to the _strvals_ 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.