CVE-2025-26620 identifies a vulnerability within the Duende.AccessTokenManagement libraries, which manage OAuth and OpenId Connect access tokens. This vulnerability allows for a race condition when requesting access tokens using the client credentials flow. In cases where concurrent requests are made with differing protocol parameters, access tokens can be returned with incorrect scope or parameters. While this issue is somewhat atypical, it poses a risk to organizations that implement these libraries under specific conditions.
The CVSS score for this vulnerability is 6.3, classifying it as medium severity. Organizations need to understand that the potential risk includes returning access tokens that do not correspond to the intended permissions. The likelihood of exploitation is contingent upon the specific implementation and usage of the libraries, particularly for those with advanced configurations.
As of now, there are no known exploits available, and the CVE has not been classified under the Known Exploited Vulnerabilities (KEV) catalog. It is essential for users of Duende.AccessTokenManagement to prioritize an update to the latest version of the NuGet package, which addresses this vulnerability, to mitigate potential risks.
Given the nature of this vulnerability, organizations should evaluate their configurations and consider potential impacts on their applications. Users employing advanced request customizations may be more susceptible and should take proactive measures to ensure that their implementations are secure.
Vulnerability Details
The vulnerability in question arises from a race condition in the Duende.AccessTokenManagement library when using the client credentials flow. Specifically, it can lead to concurrent requests returning the same access token, even if the requests differ in terms of protocol parameters. This vulnerability is particularly concerning when requests are made through the methods `HttpContext.GetClientAccessTokenAsync()` and `IClientCredentialsTokenManagementService.GetAccessTokenAsync()`.
The official CVE description emphasizes that while the race condition may affect only a small percentage of users, it can have significant implications depending on the security architecture of the application. Most users configuring the client credentials flow in a simple manner are likely to remain unaffected.
The vulnerability has been assigned a CVSS score of 6.3, indicating a medium severity level, with an attack vector classified as network, low attack complexity, and no privileges required for exploitation. The impacts on confidentiality and integrity are both rated as low.
The vulnerability was published on February 18, 2025, and is classified under CWE-367, which relates to a time-of-check to time-of-use (TOCTOU) race condition.
Technical Analysis
The root cause of this vulnerability is the race condition that occurs during concurrent access token requests. When multiple requests are made simultaneously with different `TokenRequestParameters`, the library fails to properly manage the state, resulting in the same token being issued for all requests. This can lead to unintended access and permissions being granted.
The attack vector is network-based, meaning that an attacker could potentially exploit this issue if they can make multiple requests to the service. The attack complexity is low, as no special conditions must be met for the attack to succeed, and no user interaction is required. The vulnerability does not require any privileges, making it accessible to unauthenticated users.
The impacts on confidentiality and integrity are both rated as low, indicating that while an unauthorized access token can be generated, it would mostly depend on the application logic and specific resource policies in place. Therefore, the overall impact of this vulnerability can vary significantly based on the environment and application architecture.
Organizations using the affected libraries should conduct a thorough review of their implementations to identify any reliance on concurrent access token requests with varying parameters. In many cases, a simple upgrade to the latest NuGet package should mitigate the vulnerability.
Risk & Impact Analysis
Risk to organizations includes the potential for unauthorized access if an access token is issued with incorrect permissions. The blast radius of this vulnerability is somewhat limited to users who implement advanced configurations of the Duende.AccessTokenManagement libraries, thereby affecting a smaller subset of users.
Organizations should prioritize an analysis of their usage of these libraries to determine if they are affected by this vulnerability. The urgency for patching is classified as moderate, given that a patch is available and can be applied with relative ease for most users.
As the CVSS score indicates a medium severity, organizations should address this vulnerability in their priority patch cycle. Monitoring and reviewing application logs for any anomalies related to token requests could provide additional insights into potential exploitation.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
All versions prior to vendor patch are potentially affected by this vulnerability. Users should check for updates to the Duende.AccessTokenManagement library to ensure they are using a secure version.
Mitigation & Remediation
Organizations should prioritize the application of the latest patches for the Duende.AccessTokenManagement library to mitigate this vulnerability. The upgrade to the latest version is straightforward for most users and addresses the race condition.
In cases where custom implementations of `IClientCredentialsTokenCache` are in use, developers will need to modify their code to inject the `ITokenRequestSynchronization` service into their implementations. This small code change will help ensure that concurrent requests are properly synchronized.
For those unable to immediately apply the patch, reviewing and limiting the use of concurrent requests with varying `TokenRequestParameters` can serve as a temporary mitigation strategy.
Monitoring application behavior for unusual patterns in access token requests may also help identify potential exploitation attempts.
Continuous security testing can also be valuable in validating the effectiveness of the applied patches and identifying any residual vulnerabilities.
Detection Guidance
Organizations should monitor their application logs for indicators of unusual access token retrieval patterns, particularly around the times when multiple concurrent requests are made.
Behavioral anomalies in token requests, such as multiple tokens being issued for the same resource within a short time frame, should be investigated.
Network signatures that indicate concurrent requests to the token endpoint with varying parameters could also serve as an early warning.
System changes, such as modifications to the `IClientCredentialsTokenCache`, should be closely monitored to ensure compliance with security best practices.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2025-26620 highlights the importance of managing concurrent requests in access token handling. Organizations should recognize the patterns represented in this vulnerability, particularly as they relate to race conditions in critical authentication mechanisms.
Security teams must take heed of such vulnerabilities as they reflect broader trends in application security, particularly within the context of OAuth and OpenID Connect implementations.
The lessons learned from this incident reinforce the need for thorough testing and validation of concurrent access scenarios. Organizations should ensure that their security measures extend beyond mere compliance to actively safeguarding against potential misuse.
Penetration testing methodology can provide valuable insights into the effectiveness of security controls and identify vulnerabilities that may have been overlooked.
In conclusion, CVE-2025-26620 serves as a reminder of the complexities involved in secure token management and the need for ongoing vigilance in application security practices.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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