# CVE-2026-16639: Internationalization Single Sign-On - Critical - Access bypass - SA-CONTRIB-2026-081

> Attackers can bypass authentication in the Drupal Internationalization Single Sign-On module, potentially gaining unauthorized access to user accounts.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Aug 2026
- **Updated:** 26 Aug 2026
- **Also known as:** DRUPAL-CONTRIB-2026-081, GHSA-p748-p4j4-gpx6

## What is CVE-2026-16639?

CVE-2026-16639 is a critical authentication bypass vulnerability in Drupal Internationalization Single Sign-On, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Authentication Bypass Using an Alternate Path or Channel vulnerability in Drupal Internationalization Single Sign-On allows Authentication Bypass. This issue affects Internationalization Single Sign-On versions: from 0.0.0 to 1.8.0.

Weakness: CWE-288 (Authentication Bypass Using an Alternate Path or Channel)

## Which versions are affected by CVE-2026-16639?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `drupal/i18n_sso` | Packagist:https://packages.drupal.org/8 | All versions | 1.8.0 |

## How do I fix CVE-2026-16639?

Upgrade to a fixed version.

## Is CVE-2026-16639 being exploited?

There is no known exploitation of CVE-2026-16639 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-16639 and fix it if it is affected.

What it is: CVE-2026-16639 is a critical authentication bypass vulnerability in Drupal Internationalization Single Sign-On, published on 25 Aug 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-2026-16639 in the wild and no public exploit code.

Affected product: Drupal Internationalization Single Sign-On. 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-2026-16639/ (Markdown: https://insights.sbomify.com/CVE-2026-16639/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-16639
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-16639
- OSV: https://osv.dev/vulnerability/CVE-2026-16639

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-16639/
Summaries are generated and may contain mistakes; the official description above is the record.