Summary
Improper Handling of Exceptional Conditions in Newtonsoft.Json
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.**
Impact
CVE-2024-21907 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (13.0.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2024-21907? CVE-2024-21907 is a high-severity security vulnerability in Newtonsoft.Json (nuget), affecting versions < 13.0.1. It is fixed in 13.0.1.
- How severe is CVE-2024-21907? CVE-2024-21907 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of Newtonsoft.Json are affected by CVE-2024-21907? Newtonsoft.Json (nuget) versions < 13.0.1 is affected.
- Is there a fix for CVE-2024-21907? Yes. CVE-2024-21907 is fixed in 13.0.1. Upgrade to this version or later.
- Is CVE-2024-21907 exploitable, and should I be worried? Whether CVE-2024-21907 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2024-21907 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2024-21907? Upgrade
Newtonsoft.Jsonto 13.0.1 or later.