CVE-2026-82755
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.
Does this matter?
Lower severity and a low EPSS score (0.37%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 4.0
- 6.3 MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.37% probability · 30th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-524
- Source
- 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
References
- https://cna.erlef.org/cves/CVE-2026-82755.html
- https://github.com/ash-project/ash_authentication_oauth2_server/commit/768d87f70e4e97ae1d2bf1606b5bf3f4d03f24a1
- https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-crqf-7m54-4hgc
- https://osv.dev/vulnerability/EEF-CVE-2026-82755
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.