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Gitea: OIDC userinfo Endpoint Returns Identity Claims Without Enforcing API Token Scopes

Moderate severity GitHub Reviewed Published Jul 13, 2026 in go-gitea/gitea • Updated Jul 21, 2026

Package

gomod code.gitea.io/gitea (Go)

Affected versions

< 1.27.0

Patched versions

1.27.0

Description

Summary

The OIDC userinfo endpoint (GET /login/oauth/userinfo) accepts Gitea API tokens as bearer credentials but does not enforce API token scopes before returning identity claims.

A personal access token scoped only to read:misc can successfully retrieve user information from the OIDC userinfo endpoint, even though the same token is denied access to user-related REST API endpoints that enforce scope checks.

As a result, identity information remains accessible through the OIDC endpoint regardless of the scopes assigned to the API token.

Details

Gitea supports scoped personal access tokens and enforces scope checks on user-related REST API endpoints.

For example, a token scoped only to read:misc is denied access to endpoints such as:

Endpoint Required Scope
GET /api/v1/user read:user
GET /api/v1/user/emails read:user
GET /api/v1/user/orgs read:organization

Requests to these endpoints return:

403 Forbidden

with a scope-related error.

However, the same read:misc token can be supplied as a bearer credential to:

GET /login/oauth/userinfo
Authorization: Bearer <token>

and receives a successful response containing identity claims.

Observed claims include:

  • email
  • groups

The groups claim contains organization and team membership information associated with the authenticated user.

This behavior indicates that the OIDC userinfo endpoint accepts API tokens but does not apply scope restrictions before returning identity claims.

PoC

PoC Details

Proof-of-concept code:
https://anonymous.4open.science/r/Gitea_PoC-EC93/3_poc_oidc_userinfo_scope_bypass

Reproduction Steps

  1. Create a personal access token with only the following scope:
read:misc
  1. Verify that the token cannot access user-related REST API endpoints:
GET /api/v1/user
GET /api/v1/user/emails
GET /api/v1/user/orgs

Each request returns:

403 Forbidden
  1. Send the same token to the OIDC userinfo endpoint:
GET /login/oauth/userinfo
Authorization: Bearer <read-misc-token>
  1. Observe that the request succeeds and returns identity claims, for example:
{
  "email": "user@example.com",
  "groups": [
    ...
  ]
}

Impact

Holders of narrowly scoped API tokens can obtain identity information through the OIDC userinfo endpoint regardless of the scopes assigned to the token.

The issue does not provide access to repositories, issues, pull requests, administrative functionality, or data belonging to other users.

Impact is limited to disclosure of identity information associated with the authenticated user. However, it weakens the authorization boundary established by API token scopes because identity claims remain accessible even when the token lacks user- or organization-related scopes.

References

@bircni bircni published to go-gitea/gitea Jul 13, 2026
Published to the GitHub Advisory Database Jul 21, 2026
Reviewed Jul 21, 2026
Last updated Jul 21, 2026

Severity

Moderate

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 Low
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity None
Availability None
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:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS score

Weaknesses

Exposure of Sensitive Information to an Unauthorized Actor

The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. Learn more on MITRE.

CVE ID

CVE-2026-55982

GHSA ID

GHSA-mg4f-x9v4-6h2p

Source code

Credits

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