Use of Cache Containing Sensitive Information vulnerability in ash-project ash_authentication_oauth2_server allows a shared HTTP cache to serve one tenant's OAuth discovery metadata to another tenant's clients.
The RFC 8414 and RFC 9728 metadata endpoints in AshAuthentication.Phoenix.Oauth2Server.ProtocolRouter return tenant-specific values (issuer, authorization_endpoint, token_endpoint, jwks_uri) when a tenant is set, but sent them with Cache-Control: public, max-age=3600 and no Vary. When the tenant is derived from something other than the URL (a header or the Host) and a shared cache sits in front, the cache key is the URL alone, so a stored response for one tenant is served to another for up to an hour. Affected clients may then send authorization codes and secrets to the wrong tenant's token endpoint and validate tokens against the wrong keys.
This issue affects ash_authentication_oauth2_server: from 0.1.3 before 0.3.1.
The RFC 8414 and RFC 9728 metadata endpoints in AshAuthentication.Phoenix.Oauth2Server.ProtocolRouter return tenant-specific values (issuer, authorization_endpoint, token_endpoint, jwks_uri) when a tenant is set, but sent them with Cache-Control: public, max-age=3600 and no Vary. When the tenant is derived from something other than the URL (a header or the Host) and a shared cache sits in front, the cache key is the URL alone, so a stored response for one tenant is served to another for up to an hour. Affected clients may then send authorization codes and secrets to the wrong tenant's token endpoint and validate tokens against the wrong keys.
This issue affects ash_authentication_oauth2_server: from 0.1.3 before 0.3.1.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| ash-project | ash_authentication_oauth2_server | unaffected |
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| ash-project | ash_authentication_oauth2_server | unaffected |
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Mon, 07 Sep 2026 22:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | Use of Cache Containing Sensitive Information vulnerability in ash-project ash_authentication_oauth2_server allows a shared HTTP cache to serve one tenant's OAuth discovery metadata to another tenant's clients. The RFC 8414 and RFC 9728 metadata endpoints in AshAuthentication.Phoenix.Oauth2Server.ProtocolRouter return tenant-specific values (issuer, authorization_endpoint, token_endpoint, jwks_uri) when a tenant is set, but sent them with Cache-Control: public, max-age=3600 and no Vary. When the tenant is derived from something other than the URL (a header or the Host) and a shared cache sits in front, the cache key is the URL alone, so a stored response for one tenant is served to another for up to an hour. Affected clients may then send authorization codes and secrets to the wrong tenant's token endpoint and validate tokens against the wrong keys. This issue affects ash_authentication_oauth2_server: from 0.1.3 before 0.3.1. | |
| Title | ash_authentication_oauth2_server serves tenant-specific OAuth metadata as publicly cacheable without Vary, enabling cross-tenant confusion | |
| First Time appeared |
Ash-project
Ash-project ash Authentication Oauth2 Server |
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| Weaknesses | CWE-524 | |
| CPEs | cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Ash-project
Ash-project ash Authentication Oauth2 Server |
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| Metrics |
cvssV4_0
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MITRE
Status: PUBLISHED
Assigner: EEF
Published:
Updated: 2026-09-07T22:28:24.500Z
Reserved: 2026-08-31T01:00:10.817Z
Link: CVE-2026-82755
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