# CVE-2026-82755 — ash-project ash_authentication_oauth2_server

> As of 2026-09-08, CVE-2026-82755 is a Medium-severity (band derived from the CVSS v4.0 score, not stated by the CNA) vulnerability in ash-project ash_authentication_oauth2_server, CVSS v4.0 6.3, EPSS 0.3% (29.7th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-82755 as of 2026-09-08; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-09-08

## What is 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. 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 record classifies CVE-2026-82755 under weakness class [CWE-524](https://cwe.mitre.org/data/definitions/524.html). 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 28 days ago.

## Severity and exploitation probability

- **CVSS v4.0 base score:** 6.3 — Medium (derived from score) (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:L/SA:N`)
- **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 29.7% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-09-07, last modified 2026-09-08

## Is CVE-2026-82755 being exploited?

It currently carries a trending score of 37 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [ash-project](https://intel.threadlinqs.com/vendors/ash-project): ash_authentication_oauth2_server

## How to fix CVE-2026-82755

No vendor patch reference has been recorded for CVE-2026-82755 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-82755

No threat campaign in the Threadlinqs corpus currently references CVE-2026-82755, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, FIRST EPSS. Last verified by Threadlinqs on 2026-09-08.

**Vendor advisory and patch**

- [github.com — vendor advisory](https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-crqf-7m54-4hgc)
- [github.com — patch](https://github.com/ash-project/ash_authentication_oauth2_server/commit/768d87f70e4e97ae1d2bf1606b5bf3f4d03f24a1)

**Other references**

- [cna.erlef.org — related](https://cna.erlef.org/cves/CVE-2026-82755.html)
- [osv.dev — related](https://osv.dev/vulnerability/EEF-CVE-2026-82755)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-82755
Full detection coverage and IOCs for threats exploiting CVE-2026-82755 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp