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GHSA-v9xq-2mvm-x8xc

LowCVSS 3.1 / 10
Published Oct 28, 2024·Last modified Oct 28, 2024
Affected Components(0)

No affected components available

Description

Impact

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.

Are you affected?

This vulnerability only affects IdentityServer implementations that are using the local APIs feature of IdentityServer and have explicitly enabled DPoP for local APIs. The local api authentication handler is configured with a call to either AddLocalApi or AddLocalApiAuthentication, and the opt-in to DPoP for local APIs is enabled via the TokenMode option.

Vulnerable implementations of IdentityServer would have configuration code similar to the following:

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

Patches

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.

Risk Scores
Base Score
3.1

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information.

Threat Intelligence
2.9

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
0.32%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Low severity
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