# CVE-2026-74864: Authentication Bypass in sogo_yhn

> Attackers can bypass authentication by injecting a specific HTTP header, gaining unauthorized access to any user account, including privileged ones.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/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:** No
- **Published:** 30 Sep 2026
- **Updated:** 30 Sep 2026
- **Also known as:** GHSA-fxx9-8vhm-fwhc

## What is CVE-2026-74864?

CVE-2026-74864 is a critical authentication bypass vulnerability in YunoHost-Apps sogo_yhn, published on 30 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

sogo_yhn configures SOGo with a parameter that forces the request with HTTP header "x-webobjects-remote-user" to be treated as sent by a verified user without performing password validation. Since Nginx does not strip this header, any client can supply it arbitrarily and gain access as any user, including a privileged user, without providing a password.

This issue was fixed in version 5.8.0~ynh9.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-74864?


## How do I fix CVE-2026-74864?

No fix has been published for CVE-2026-74864 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-74864 being exploited?

There is no known exploitation of CVE-2026-74864 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74864 and fix it if it is affected.

What it is: CVE-2026-74864 is a critical authentication bypass vulnerability in YunoHost-Apps sogo_yhn, published on 30 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-2026-74864 in the wild and no public exploit code.

Affected product: YunoHost-Apps sogo_yhn. 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-2026-74864/ (Markdown: https://insights.sbomify.com/CVE-2026-74864/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74864
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74864
- OSV: https://osv.dev/vulnerability/CVE-2026-74864

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74864/
Summaries are generated and may contain mistakes; the official description above is the record.