# CVE-2026-80218: Sign-in token minted for one resource accepted by another in AshAuthentication

> Attackers can use a sign-in token from one resource to authenticate as a user on a different resource due to improper JWT subject validation.

- **Severity:** High 7.6 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** EEF-CVE-2026-80218, GHSA-3pr8-f99q-86hp

## What is CVE-2026-80218?

CVE-2026-80218 is a high-severity authentication bypass vulnerability in team-alembic ash_authentication, published on 17 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Improper Authentication vulnerability in team-alembic AshAuthentication allows an attacker holding a sign-in token for one authenticated resource to be signed in as a user of a different resource.

AshAuthentication.Strategy.Password.SignInWithTokenPreparation.extract_primary_keys_from_subject/2 parses the JWT sub claim (for example user?id=1) with URI.parse/1 and keeps only its query string, discarding the path segment that names the subject the token was issued for. Nothing else restores that binding: AshAuthentication.Jwt.verify/3 checks the signature, exp, nbf, jti and the library-version claims, the purpose check only requires sign_in, and the remaining comparison is over primary-key field names, which are identical across resources. The WebAuthn sign-in and remember-me preparations carry copies of the same helper and drop the path in the same way. The magic link sign-in path pins the subject name against the resource and is not affected.

This issue affects ash_authentication: from 3.10.5 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-80218?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ash_authentication` | Hex | From 3.10.5 | 4.15.0, 5.0.0-rc.14 |

## How do I fix CVE-2026-80218?

Upgrade ash_authentication to a fixed version for your release line: 4.15.0 or 5.0.0-rc.14.

## Is CVE-2026-80218 being exploited?

There is no known exploitation of CVE-2026-80218 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80218 and fix it if it is affected.

What it is: CVE-2026-80218 is a high-severity authentication bypass vulnerability in team-alembic ash_authentication, published on 17 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-80218 in the wild and no public exploit code.

Affected packages and fixed versions:
- ash_authentication (Hex): affected from 3.10.5; fixed in 4.15.0, 5.0.0-rc.14

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-2026-80218/ (Markdown: https://insights.sbomify.com/CVE-2026-80218/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80218
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80218
- OSV: https://osv.dev/vulnerability/CVE-2026-80218

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80218/
Summaries are generated and may contain mistakes; the official description above is the record.