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AWS Cloud Development Kit (AWS CDK) IAM OIDC custom resource allows connection to unauthorized OIDC provider

Low severity GitHub Reviewed Published Jan 17, 2025 in aws/aws-cdk • Updated Jan 17, 2025

Package

npm aws-cdk-lib (npm)

Affected versions

<= 2.176.0

Patched versions

None

Description

Impact

Users who use IAM OIDC custom resource provider package will download CA Thumbprints as part of the custom resource workflow, /~https://github.com/aws/aws-cdk/blob/d16482fc8a4a3e1f62751f481b770c09034df7d2/packages/%40aws-cdk/custom-resource-handlers/lib/aws-iam/oidc-handler/external.ts#L34.

However, the current tls.connect method will always set rejectUnauthorized: false which is a potential security concern. CDK should follow the best practice and set rejectUnauthorized: true. However, this could be a breaking change for existing CDK applications and we should fix this with a feature flag.

Note that this is marked as low severity Security advisory because the issuer url is provided by CDK users who define the CDK application. If they insist on connecting to a unauthorized OIDC provider, CDK should not disallow this. Additionally, the code block is run in a Lambda environment which mitigate the MITM attack.

As a best practice, CDK should still fix this issue under a feature flag to avoid regression.

packages/@aws-cdk/custom-resource-handlers/lib/aws-iam/oidc-handler/external.ts
❯❱ problem-based-packs.insecure-transport.js-node.bypass-tls-verification.bypass-tls-verification
Checks for setting the environment variable NODE_TLS_REJECT_UNAUTHORIZED to 0, which disables TLS
verification. This should only be used for debugging purposes. Setting the option rejectUnauthorized
to false bypasses verification against the list of trusted CAs, which also leads to insecure
transport.

Patches

The patch is in progress. To mitigate, upgrade to CDK v2.177.0 (Expected release date 2025-02-22).
Once upgraded, please make sure the feature flag '@aws-cdk/aws-iam:oidcRejectUnauthorizedConnections' is set to true in cdk.context.json or cdk.json. More details on feature flag setting is here.

Workarounds

N/A

References

aws/aws-cdk#32920

References

@GavinZZ GavinZZ published to aws/aws-cdk Jan 17, 2025
Published by the National Vulnerability Database Jan 17, 2025
Published to the GitHub Advisory Database Jan 17, 2025
Reviewed Jan 17, 2025
Last updated Jan 17, 2025

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity High
Attack Requirements Present
Privileges Required High
User interaction Active
Vulnerable System Impact Metrics
Confidentiality Low
Integrity Low
Availability Low
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Weaknesses

CVE ID

CVE-2025-23206

GHSA ID

GHSA-v4mq-x674-ff73

Source code

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