A08 — Software or Data Integrity Failures

Data integrity failures occur when code deserializes untrusted data without type restrictions, allowing attackers to instantiate arbitrary types and execute code. These rules detect the most dangerous .NET deserialization patterns.

OWASPA08001 — BinaryFormatter usage

Property	Value
Severity	Error
Category	A08 Software or Data Integrity Failures

What it detects

Any use of BinaryFormatter.Serialize() or BinaryFormatter.Deserialize().

Why it matters

BinaryFormatter is an inherently unsafe serializer. Deserializing attacker-controlled data with BinaryFormatter allows arbitrary code execution (RCE) via gadget chains. Microsoft has disabled it by default in .NET 5+ and it will throw by default in modern .NET.

❌ Non-compliant

var formatter = new BinaryFormatter();
var obj = formatter.Deserialize(stream);

✅ Compliant

Use a safe alternative:

// For general data: System.Text.Json or Newtonsoft.Json
var obj = JsonSerializer.Deserialize<MyType>(stream);

// For binary: MessagePack, Protobuf-net, or similar
var obj = MessagePackSerializer.Deserialize<MyType>(stream);

---

OWASPA08002 — Unsafe deserializer (NetDataContractSerializer / SoapFormatter)

Property	Value
Severity	Error
Category	A08 Software or Data Integrity Failures

What it detects

Use of NetDataContractSerializer or SoapFormatter, both of which deserialize arbitrary types and are vulnerable to the same gadget-chain attacks as BinaryFormatter.

❌ Non-compliant

var serializer = new NetDataContractSerializer();
var obj = serializer.ReadObject(stream);

✅ Compliant

var obj = JsonSerializer.Deserialize<MyType>(stream);

---

OWASPA08003 — TypeNameHandling in Newtonsoft.Json

Property	Value
Severity	Error
Category	A08 Software or Data Integrity Failures

What it detects

JsonSerializerSettings with TypeNameHandling set to any value other than None.

Why it matters

When TypeNameHandling is not None, Newtonsoft.Json embeds .NET type names in the JSON and instantiates them during deserialization. This allows attackers who control the JSON to instantiate any type in the process, leading to RCE via known .NET gadget chains.

❌ Non-compliant

var settings = new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.All  // ❌ RCE risk
};
var obj = JsonConvert.DeserializeObject(json, settings);

✅ Compliant

var settings = new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.None  // default, safe
};
// Or use System.Text.Json which does not support TypeNameHandling
var obj = JsonSerializer.Deserialize<MyType>(json);

---

OWASPA08004 — JavaScriptSerializer with SimpleTypeResolver

Property	Value
Severity	Error
Category	A08 Software or Data Integrity Failures

What it detects

JavaScriptSerializer instantiated with a SimpleTypeResolver, which enables polymorphic type resolution and RCE via gadget chains.

❌ Non-compliant

var serializer = new JavaScriptSerializer(new SimpleTypeResolver());
var obj = serializer.Deserialize<object>(json);

✅ Compliant

// JavaScriptSerializer without a type resolver is safer, but prefer:
var obj = JsonSerializer.Deserialize<MyType>(json);

JavaScriptSerializer is a legacy API. Prefer System.Text.Json for all new code.