# CVE-2026-42560: auth: Patreon provider assigns the same local user ID to every authenticated Patreon account, enabling cross‑user impersonation

> The Patreon OAuth provider assigns identical local IDs to all users, allowing attackers to impersonate others and access their accounts.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 May 2026
- **Updated:** 11 May 2026
- **Also known as:** GHSA-f6qq-3m3h-4g42, GO-2026-5348

## What is CVE-2026-42560?

CVE-2026-42560 is a critical authentication bypass vulnerability in go-pkgz auth, published on 9 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

auth provides authentication via oauth2, direct and email. From versions 1.18.0 to before 1.25.2 and 2.0.0 to before 2.1.2, the Patreon OAuth provider maps every authenticated Patreon account to the same local user.ID, instead of deriving a unique ID from the Patreon account returned by Patreon. In practice, this means all Patreon-authenticated users of an application using this library are collapsed into a single local identity. Any application that trusts token.User.ID as the stable account key can end up mixing or fully merging unrelated Patreon users, which can lead to cross-account access, privilege confusion, and subscription-state leakage. This issue has been patched in versions 1.25.2 and 2.1.2.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-42560?

6 open source packages ship an affected version, including github.com/go-pkgz/auth and github.com/go-pkgz/auth/v2.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/go-pkgz/auth` | Go | From 1.18.0 | 1.25.2 |
| `github.com/go-pkgz/auth` | Go | From 1.18.0 | 1.25.2 |
| `github.com/go-pkgz/auth` | Go | From 1.18.0 | 1.25.2 |
| `github.com/go-pkgz/auth/v2` | Go | From 2.0.0 | 2.1.2 |
| `github.com/go-pkgz/auth/v2` | Go | From 2.0.0 | 2.1.2 |
| `github.com/go-pkgz/auth/v2` | Go | From 2.0.0 | 2.1.2 |

## How do I fix CVE-2026-42560?

Upgrade github.com/go-pkgz/auth to 1.25.2 or later.

## Is CVE-2026-42560 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42560 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42560 and fix it if it is affected.

What it is: CVE-2026-42560 is a critical authentication bypass vulnerability in go-pkgz auth, published on 9 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42560 exists.

Affected packages and fixed versions:
- github.com/go-pkgz/auth (Go): affected from 1.18.0; fixed in 1.25.2
- github.com/go-pkgz/auth (Go): affected from 1.18.0; fixed in 1.25.2
- github.com/go-pkgz/auth (Go): affected from 1.18.0; fixed in 1.25.2
- github.com/go-pkgz/auth/v2 (Go): affected from 2.0.0; fixed in 2.1.2
- github.com/go-pkgz/auth/v2 (Go): affected from 2.0.0; fixed in 2.1.2
- github.com/go-pkgz/auth/v2 (Go): affected from 2.0.0; fixed in 2.1.2

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-2026-42560/ (Markdown: https://insights.sbomify.com/CVE-2026-42560/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42560
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42560
- OSV: https://osv.dev/vulnerability/CVE-2026-42560

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42560/
Summaries are generated and may contain mistakes; the official description above is the record.