CVE-2026-86698 in hexpm
Summary
by MITRE • 09/22/2026
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.
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Analysis
by VulDB Data Team • 09/22/2026
The vulnerability identified in hexpm represents a critical flaw in session management and access control enforcement within the OAuth token issuance workflow, specifically affecting how refresh tokens are handled for private repository access. This issue allows users who have had their organization membership revoked or whose sessions terminated to retain read-only access to private packages and documentation tarballs through retained refresh tokens that remain valid for up to thirty days. The root cause lies in the implementation of the generate_refresh_token function within the lib/hexpm/oauth/jwt module, which signs refresh tokens using identical issuer, audience, and scope claims as those used for short-lived access tokens. Consequently, these refresh tokens carry repository-specific scopes such as repository:<org> that mirror the permissions granted at the time of issuance without any mechanism to distinguish between transient access tokens and long-term refresh tokens during validation processes.
The operational impact stems from a fundamental architectural weakness in how the CDN service validates authorization requests for private repositories. When serving content, the CDN verifies only the cryptographic signature and expiration claims present in presented tokens while deriving authorization decisions solely from scope claims embedded within those tokens. This design eliminates any database lookup or real-time verification of current user status against organizational membership records. As a result, when an administrator removes a member from an organization or revokes their active session through standard administrative controls, these changes do not propagate to the CDN layer until the thirty-day refresh token naturally expires rather than taking immediate effect after the typical thirty-minute access token lifetime concludes. This creates a significant window of opportunity where unauthorized individuals can continue accessing sensitive proprietary codebases and technical documentation despite having lost legitimate organizational standing.
From a security classification perspective, this vulnerability aligns with CWE-613 which addresses insufficient session expiration due to improper invalidation mechanisms during authentication processes. The flaw also maps directly to MITRE ATT&CK technique T1078.2 representing Valid Accounts within specific environments since attackers can leverage previously authenticated credentials that remain functionally active despite administrative revocation actions. Additionally, the lack of real-time validation against central identity sources corresponds to CWE-640 which describes weakness in relying on client-side state rather than server-side verification for authorization decisions. These classifications highlight how the vulnerability enables persistent unauthorized access through technically valid but logically expired credentials that bypass intended security controls designed to limit exposure windows following membership termination or session invalidation events.
The severity of this issue is compounded by its read-only nature which, while limiting direct data modification risks, still exposes valuable intellectual property including proprietary source code repositories and internal technical documentation tarballs to former employees or compromised accounts whose access should have been immediately terminated upon organizational departure or security incident response actions. The thirty-day retention period effectively creates a prolonged exposure window where sensitive information remains accessible without proper oversight or audit trails indicating unauthorized continued usage patterns that might otherwise trigger additional security investigations.
Mitigation strategies must address both the immediate technical flaw and broader architectural improvements to prevent similar vulnerabilities in future implementations. Immediate remediation requires modifying the token validation logic within the CDN service layer to implement real-time verification against central identity providers rather than relying exclusively on static scope claims embedded within JWT tokens. This involves integrating database lookups or cache-based status checks that confirm current organizational membership status before granting access to private repository content regardless of whether presented credentials appear cryptographically valid and temporally unexpired according to their own internal timestamps.
Long-term architectural improvements should include implementing token binding mechanisms that associate refresh tokens with specific device fingerprints or IP address ranges requiring re-authentication upon significant environmental changes. Additionally, adopting shorter refresh token lifespans combined with automatic rotation policies would reduce the window of opportunity for unauthorized access while maintaining reasonable user experience standards. Implementing comprehensive audit logging for all private repository access events regardless of authentication method employed enables security teams to detect anomalous usage patterns indicative of lingering unauthorized access attempts stemming from expired credentials that have not yet been properly invalidated across distributed service layers.
The affected version range spans from October tenth twenty twenty five through September twenty second twenty twenty six indicating a defined period during which systems operating hexpm infrastructure remain vulnerable until patches implementing these architectural corrections are deployed and validated across all CDN edge nodes serving private repository content to ensure consistent enforcement of access control policies aligned with current organizational membership records rather than historical token issuance states.