# CVE-2026-13543: Documenso Google OAuth Login handle-oauth-callback-url.ts improper authentication

> Attackers can bypass authentication in Documenso's Google OAuth callback, potentially taking over user accounts.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 29 Jun 2026
- **Updated:** 29 Jun 2026
- **Also known as:** GHSA-3hjr-gmh6-w2qr

## What is CVE-2026-13543?

CVE-2026-13543 is a medium-severity authentication bypass vulnerability in Documenso, published on 29 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability was detected in Documenso up to 2.11.0. Affected by this vulnerability is an unknown functionality of the file packages/auth/server/lib/utils/handle-oauth-callback-url.ts of the component Google OAuth Login. The manipulation results in improper authentication. It is possible to launch the attack remotely. This attack is characterized by high complexity. The exploitation appears to be difficult. The exploit is now public and may be used. The pull request to fix this issue awaits acceptance.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-13543?


## How do I fix CVE-2026-13543?

No fix has been published for CVE-2026-13543 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-13543 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-13543 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-13543 and fix it if it is affected.

What it is: CVE-2026-13543 is a medium-severity authentication bypass vulnerability in Documenso, published on 29 Jun 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-2026-13543 exists.

Affected product: Documenso. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-13543/ (Markdown: https://insights.sbomify.com/CVE-2026-13543/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-13543
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-13543
- OSV: https://osv.dev/vulnerability/CVE-2026-13543

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-13543/
Summaries are generated and may contain mistakes; the official description above is the record.