Summary
When parseBody() expands dot-separated form field names into nested objects, it does not limit the nesting depth or the total number of objects created. A request body well within a normal size limit can therefore allocate an object graph far larger than the request itself, and concurrent requests can exhaust the heap and terminate the process.
Details
Each dot-separated segment of a field name creates an intermediate object. Neither the segments within a single field name nor the total across a request was bounded, and empty segments were preserved, so a field name could encode one nesting level per byte.
Both shapes produce the effect: a single deeply dotted field name, and a large number of shallowly dotted ones within one body. A request body size limit does not prevent it, because the amplification happens after the body has been accepted.
Dot-notation parsing is not enabled by default.
Impact
An attacker who can reach an endpoint that parses request bodies with dot-notation enabled can send concurrent requests whose memory cost is disproportionate to their size.
This may lead to:
- exhaustion of the JavaScript heap and termination of the server process
- the service remaining unavailable until it is restarted
This issue affects applications that explicitly enable dot-notation parsing. Applications using the default behaviour are not affected.
References
Rikuxx0 Reporter
Summary
When
parseBody()expands dot-separated form field names into nested objects, it does not limit the nesting depth or the total number of objects created. A request body well within a normal size limit can therefore allocate an object graph far larger than the request itself, and concurrent requests can exhaust the heap and terminate the process.Details
Each dot-separated segment of a field name creates an intermediate object. Neither the segments within a single field name nor the total across a request was bounded, and empty segments were preserved, so a field name could encode one nesting level per byte.
Both shapes produce the effect: a single deeply dotted field name, and a large number of shallowly dotted ones within one body. A request body size limit does not prevent it, because the amplification happens after the body has been accepted.
Dot-notation parsing is not enabled by default.
Impact
An attacker who can reach an endpoint that parses request bodies with dot-notation enabled can send concurrent requests whose memory cost is disproportionate to their size.
This may lead to:
This issue affects applications that explicitly enable dot-notation parsing. Applications using the default behaviour are not affected.
References