# CVE-2026-82754: ash_authentication_oauth2_server aliases every protocol endpoint under /.well-known, bypassing path-scoped controls

> Attackers can bypass WAF rules and rate limits by accessing OAuth endpoints via /.well-known aliases instead of /oauth paths.

- **Severity:** Medium 6.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Sep 2026
- **Updated:** 8 Sep 2026
- **Also known as:** EEF-CVE-2026-82754, GHSA-wwxg-h779-3wf4

## What is CVE-2026-82754?

CVE-2026-82754 is a medium-severity vulnerability in ash-project ash_authentication_oauth2_server, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-424 (Improper Protection of Alternate Path)

## Which versions are affected by CVE-2026-82754?

1 open source package ship an affected version, including ash_authentication_oauth2_server.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ash_authentication_oauth2_server` | Hex | From 0.1.0 | 0.3.1 |

## How do I fix CVE-2026-82754?

Upgrade ash_authentication_oauth2_server to 0.3.1 or later.

## Is CVE-2026-82754 being exploited?

There is no known exploitation of CVE-2026-82754 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-82754 and fix it if it is affected.

What it is: CVE-2026-82754 is a medium-severity vulnerability in ash-project ash_authentication_oauth2_server, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-82754 in the wild and no public exploit code.

Affected packages and fixed versions:
- ash_authentication_oauth2_server (Hex): affected from 0.1.0; fixed in 0.3.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-82754/ (Markdown: https://insights.sbomify.com/CVE-2026-82754/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-82754
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-82754
- OSV: https://osv.dev/vulnerability/CVE-2026-82754

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-82754/
Summaries are generated and may contain mistakes; the official description above is the record.