CVE-2021-29508

Insecure deserialization in Wire

Due to how Wire handles type information in its serialization format, malicious payloads can be passed to a deserializer. e.g. using a surrogate on the sender end, an attacker can pass information about a different type for the receiving end. And by doing so allowing the serializer to create any type on the deserializing end.

This is the same issue that exists for .NET BinaryFormatter https://docs.microsoft.com/en-us/visualstudio/code-quality/ca2300?view=vs-2019

This also applies to the fork of Wire, AkkaDotNet/Hyperion.

Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect. Typical impact: arbitrary code execution or logic abuse.

CVE-2021-29508 has a CVSS score of 9.1 (Critical). 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. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

Already deployed Kodem?

1. What is CVE-2021-29508? CVE-2021-29508 is a critical-severity insecure deserialization vulnerability in Wire (nuget), affecting versions <= 1.0.0. No fixed version is listed yet. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
2. How severe is CVE-2021-29508? CVE-2021-29508 has a CVSS score of 9.1 (Critical). 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.
3. Which versions of Wire are affected by CVE-2021-29508? Wire (nuget) versions <= 1.0.0 is affected.
4. Is there a fix for CVE-2021-29508? No fixed version is listed for CVE-2021-29508 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2021-29508 exploitable, and should I be worried? Whether CVE-2021-29508 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
6. What actually determines whether CVE-2021-29508 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.
7. How do I fix CVE-2021-29508? No fixed version is listed yet. In the interim: Avoid deserializing data from untrusted sources. If deserialization is required, use a format that does not support code execution and validate the input strictly.