# CVE-2026-82754 — ash-project ash_authentication_oauth2_server

> As of 2026-09-08, CVE-2026-82754 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% (31.6th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-82754 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-2026-82754?

Improper Protection of Alternate Path vulnerability in ash-project ash_authentication_oauth2_server exposes the state-changing OAuth endpoints under an unintended URL prefix, bypassing controls scoped to the canonical prefix. oauth2_server_protocol_routes/1 in AshAuthentication.Phoenix.Oauth2Server.Router forwards the same ProtocolRouter at both the /oauth prefix and the /.well-known prefix. Phoenix forward strips the matched prefix before dispatch, so the full route table answers under both mounts, and POST /register, POST /token, and POST /revoke are reachable as /.well-known/register, /.well-known/token, and /.well-known/revoke. Edge controls such as WAF rules, rate limits, or authentication exemptions written against the /oauth paths, or that allow-list /.well-known as unauthenticated, do not apply to the alias. This issue affects ash_authentication_oauth2_server: from 0.1.0 before 0.3.1.

The record classifies CVE-2026-82754 under weakness class [CWE-424](https://cwe.mitre.org/data/definitions/424.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:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 31.6% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.4/10 — 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-2026-82754 being exploited?

It currently carries a trending score of 38 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-2026-82754

No vendor patch reference has been recorded for CVE-2026-82754 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-2026-82754

No threat campaign in the Threadlinqs corpus currently references CVE-2026-82754, 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-wwxg-h779-3wf4)
- [github.com — patch](https://github.com/ash-project/ash_authentication_oauth2_server/commit/a72972d7ed3eb74c05dfa0653a258ef14454459a)

**Other references**

- [cna.erlef.org — related](https://cna.erlef.org/cves/CVE-2026-82754.html)
- [osv.dev — related](https://osv.dev/vulnerability/EEF-CVE-2026-82754)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-82754
Full detection coverage and IOCs for threats exploiting CVE-2026-82754 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp