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GHSA-92vj-hp7m-gwcj
Nerdbank.MessagePackImpact
Applications that call OptionalConverters.WithExpandoObjectConverter and deserialize untrusted data are open to a vulnerability by which an attacker can exploit a O(n²) algorithm to burn an inordinate amount of CPU effort by adding a great many properties to an ExpandoObject, whose Add method is implemented as an O(n) algorithm.
Patches
Update to a patched version.
If a project's ExpandoObject data requires more than 128 properties, the default limit should be changed:
this.Serializer = this.Serializer with
{
StartingContext = this.Serializer.StartingContext with
{
Security = this.Serializer.StartingContext.Security with
{
ExpandoObjectMaxPropertyCount = 256, // Set this to whatever limit is required by your application
},
},
};
Workarounds
Avoid the non-default WithExpandoObjectConverter extension method when deserializing untrusted data.
If deserializing untrusted data into an ExpandoObject is required, developers should write a custom converter for their project that limits the number of properties allowed before initializing the object.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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