CVE-2026-86698: Refresh tokens accepted as private repository credentials at the CDN

Severity: low (CVSS 2.3 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-22 · updated 2026-09-22
Weakness: CWE-613

Description

Insufficient Session Expiration vulnerability in OAuth token issuance in hexpm hexpm allows a user whose organization membership or session has ended to keep reading the organization's private packages and their documentation tarballs via a retained refresh token. generate_refresh_token/4 in lib/hexpm/oauth/jwt.ex signs the refresh token with the same iss, aud and scope claims as the access token, so it carries the same repository:<org> scopes. The CDN service that serves private repositories verifies the signature and time claims and then authorizes from the scope claim, with no database lookup and no way to tell the two token kinds apart. Removing a member or revoking a session therefore takes effect at the CDN only when the 30 day refresh token expires, instead of after the 30 minute access token lifetime. Access is read-only and limited to organizations the account belonged to when the token was granted. This issue affects hex.pm: from 2025-10-10 before 2026-09-22.

Affected products

hexpm: from 2025-10-10 before 2026-09-22 — fixed in 2026-09-22

How to fix

Upgrade to a fixed version: hexpm 2026-09-22. Check the vendor advisory for mitigations.

References

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