An API key created with read-only permissions (domain: "api", resource: "read") can be escalated to full write access under specific conditions.
When exchanging a read-only API key via the OAuth client_credentials grant, the resource qualifier is ignored. The resulting JWT receives the broad "api" scope instead of the expected "api:read" scope. This token is therefore treated as having full API access.
If an attacker is able to obtain a victim's read-only API key and a valid 2FA (TOTP) code for the victim account, they can use the incorrectly scoped JWT to create a new full-access API key with unrestricted API permissions that does not expire by default and can perform write operations such as publishing, retiring, or modifying packages.
This vulnerability is associated with program files lib/hexpm_web/controllers/api/oauth_controller.ex and program routines 'Elixir.HexpmWeb.API.OAuthController':validate_scopes_against_key/2.
This issue affects hexpm: from 71829cb6f6559bcceb1ef4e43a2fb8cdd3af654b before 71c127afebb7ed7cc637eb231b98feb802d62999.
Metrics
Affected Vendors & Products
No advisories yet.
Solution
No solution given by the vendor.
Workaround
* Revoke and reissue exposed API keys immediately if compromise is suspected. * Avoid relying on read-only API keys as a strict security boundary in high-risk environments. * Closely monitor audit logs for unexpected API key creation events. * Enforce strong 2FA hygiene and protect TOTP seeds carefully. There is no complete mitigation without upgrading, as the issue exists in server-side scope validation logic.
Thu, 05 Mar 2026 19:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | Incorrect Authorization vulnerability in hexpm hexpm/hexpm ('Elixir.HexpmWeb.API.OAuthController' module) allows Privilege Escalation. An API key created with read-only permissions (domain: "api", resource: "read") can be escalated to full write access under specific conditions. When exchanging a read-only API key via the OAuth client_credentials grant, the resource qualifier is ignored. The resulting JWT receives the broad "api" scope instead of the expected "api:read" scope. This token is therefore treated as having full API access. If an attacker is able to obtain a victim's read-only API key and a valid 2FA (TOTP) code for the victim account, they can use the incorrectly scoped JWT to create a new full-access API key with unrestricted API permissions that does not expire by default and can perform write operations such as publishing, retiring, or modifying packages. This vulnerability is associated with program files lib/hexpm_web/controllers/api/oauth_controller.ex and program routines 'Elixir.HexpmWeb.API.OAuthController':validate_scopes_against_key/2. This issue affects hexpm: from 71829cb6f6559bcceb1ef4e43a2fb8cdd3af654b before 71c127afebb7ed7cc637eb231b98feb802d62999. | |
| Title | Improper Scope Enforcement in OAuth client_credentials Flow Allows Read-Only API Key to Escalate to Full Access | |
| First Time appeared |
Hexpm
Hexpm hexpm |
|
| Weaknesses | CWE-863 | |
| CPEs | cpe:2.3:a:hexpm:hexpm:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Hexpm
Hexpm hexpm |
|
| References |
| |
| Metrics |
cvssV4_0
|
Projects
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Status: PUBLISHED
Assigner: EEF
Published:
Updated: 2026-03-05T19:20:05.831Z
Reserved: 2026-01-01T03:46:45.934Z
Link: CVE-2026-21621
No data.
Status : Received
Published: 2026-03-05T20:16:12.617
Modified: 2026-03-05T20:16:12.617
Link: CVE-2026-21621
No data.
OpenCVE Enrichment
No data.