Details

Newtonsoft.Json prior to version 13.0.1 is vulnerable to Insecure Defaults due to improper handling of expressions with high nesting level that lead to StackOverFlow exception or high CPU and RAM usage. Exploiting this vulnerability results in Denial Of Service (DoS).

The serialization and deserialization path have different properties regarding the issue.

Deserializing methods (like JsonConvert.DeserializeObject) will process the input that results in burning the CPU, allocating memory, and consuming a thread of execution. Quite high nesting level (>10kk, or 9.5MB of {a:{a:{... input) is needed to achieve the latency over 10 seconds, depending on the hardware.

Serializing methods (like JsonConvert.Serialize or JObject.ToString) will throw StackOverFlow exception with the nesting level of around 20k.

To mitigate the issue one either need to update Newtonsoft.Json to 13.0.1 or set MaxDepth parameter in the JsonSerializerSettings. This can be done globally with the following statement. After that the parsing of the nested input will fail fast with Newtonsoft.Json.JsonReaderException:

JsonConvert.DefaultSettings = () => new JsonSerializerSettings { MaxDepth = 128 };

Repro code:

//Create a string representation of an highly nested object (JSON serialized)
int nRep = 25000;
string json = string.Concat(Enumerable.Repeat("{a:", nRep)) + "1" +
 string.Concat(Enumerable.Repeat("}", nRep));

//Parse this object (leads to high CPU/RAM consumption)
var parsedJson = JsonConvert.DeserializeObject(json);

// Methods below all throw stack overflow with nRep around 20k and higher
// string a = parsedJson.ToString();
// string b = JsonConvert.SerializeObject(parsedJson);

Additional affected product and version information

The original statement about the problem only affecting IIS applications is misleading. Any application is affected, however the IIS has a behavior that stops restarting the instance after some time resulting in a harder-to-fix DoS.**

Severity

• CVSS Score: 7.5 / 10 (High)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

• https://github.com/JamesNK/Newtonsoft.Json/issues/2457
• https://github.com/JamesNK/Newtonsoft.Json/pull/2462
• https://github.com/JamesNK/Newtonsoft.Json/commit/7e77bbe1beccceac4fc7b174b53abfefac278b66
• https://alephsecurity.com/2018/10/22/StackOverflowException
• https://alephsecurity.com/vulns/aleph-2018004
• https://github.com/JamesNK/Newtonsoft.Json
• https://security.snyk.io/vuln/SNYK-DOTNET-NEWTONSOFTJSON-2774678

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

v13.0.1

Compare Source

• New feature - Add JsonSelectSettings with configuration for a regex timeout
• Change - Remove portable assemblies from NuGet package
• Change - JsonReader and JsonSerializer MaxDepth defaults to 64
• Change - Change InvalidCastException to JsonSerializationException on mismatched JToken
• Fix - Fixed throwing missing member error on ignored fields
• Fix - Fixed various nullable annotations
• Fix - Fixed annotations not being copied when tokens are cloned
• Fix - Fixed naming strategy not being used when deserializing dictionary enum keys
• Fix - Fixed serializing nullable struct dictionaries
• Fix - Fixed JsonWriter.WriteToken to allow null with string token
• Fix - Fixed missing error when deserializing JToken with a contract type mismatch
• Fix - Fixed JTokenWriter when writing comment to an object

v12.0.3

Compare Source

• New feature - Added support for nullable reference types
• New feature - Added KebabCaseNamingStrategy
• Change - Package now uses embedded package icon
• Fix - Fixed bug when merging JToken with itself
• Fix - Fixed performance of calling ICustomTypeDescriptor.GetProperties
• Fix - Fixed serializing Enumerable.Empty and empty arrays on .NET Core 3.0
• Fix - Fixed deserializing some collection types with constructor
• Fix - Fixed deserializing IImmutableSet to ImmutableHashSet instead of ImmutableSortedSet
• Fix - Fixed deserializing IImmutableDictionary to ImmutableDictionary instead of ImmutableSortedDictionary
• Fix - Fixed deserializing into constructors with more than 256 parameters
• Fix - Fixed hang when deserializing JTokenReader with preceding comment
• Fix - Fixed JSONPath scanning with nested indexer
• Fix - Fixed deserializing incomplete JSON object to JObject
• Fix - Fixed using StringEnumConverter with naming strategy and specified values

v12.0.2

Compare Source

• New feature - Added MissingMemberHandling to JsonObjectAttribute and JsonObjectContract
• New feature - Added constructor to JTokenReader to specify initial path
• New feature - Added JsonProperty.IsRequiredSpecified
• New feature - Added JsonContract.InternalConverter
• Change - Moved embedded debug symbols in NuGet package to a symbol package on NuGet.org
• Fix - Fixed deserializing nullable struct collections
• Fix - Fixed memory link when serializing enums to named values
• Fix - Fixed error when setting JsonLoadSettings.DuplicatePropertyNameHandling to Replace