CVE-2024-49755

Duende IdentityServer has insufficient validation of DPoP cnf claim in Local APIs

services.AddAuthentication()
    .AddLocalApi("local", options => 
    {
        options.TokenMode = LocalApiTokenMode.DPoPAndBearer; // or LocalApiTokenMode.DPoPOnly
    });

IdentityServer's local API authentication handler performs insufficient validation of the cnf claim in DPoP access tokens. This allows an attacker to use leaked DPoP access tokens at local api endpoints even without possessing the private key for signing proof tokens.

Note that this only impacts custom endpoints within an IdentityServer implementation that have explicitly used the LocalApiAuthenticationHandler for authentication. It does not impact:

• OAuth or OIDC protocol endpoints defined by IdentityServer, such as the authorize and token endpoints.
• Typical UI pages within an IdentityServer implementation, which are not normally authorized with the local API authentication handler.
• The use of DPoP to create sender-constrained tokens in IdentityServer that are consumed by external API resources.
• The use of DPoP to sender-constrain refresh tokens issued to public clients.

The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.

CVE-2024-49755 has a CVSS score of 3.1 (Low). The vector is network-reachable, no privileges required, and user interaction required. 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 (7.0.8); upgrading removes the vulnerable code path.

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This vulnerability is patched in IdentityServer 7.0.8. Version 6.3 and below are unaffected, as they do not support DPoP in Local APIs.

1. What is CVE-2024-49755? CVE-2024-49755 is a low-severity improper authentication vulnerability in Duende.IdentityServer (nuget), affecting versions >= 7.0.0, < 7.0.8. It is fixed in 7.0.8. The application does not adequately verify the identity of a user, device, or process before granting access.
2. How severe is CVE-2024-49755? CVE-2024-49755 has a CVSS score of 3.1 (Low). 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 Duende.IdentityServer are affected by CVE-2024-49755? Duende.IdentityServer (nuget) versions >= 7.0.0, < 7.0.8 is affected.
4. Is there a fix for CVE-2024-49755? Yes. CVE-2024-49755 is fixed in 7.0.8. Upgrade to this version or later.
5. Is CVE-2024-49755 exploitable, and should I be worried? Whether CVE-2024-49755 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-2024-49755 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-2024-49755? Upgrade Duende.IdentityServer to 7.0.8 or later.

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