# CVE-2019-3878: Auth bypass in mod auth mellon

> Attackers can bypass authentication in mod_auth_mellon by sending special SAML ECP headers when Apache is configured as a reverse proxy.

- **Severity:** High 8.1 (`CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A: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:** 26 Mar 2019
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2019-3878, GHSA-6gx9-985p-w8c8, RHSA-2019:0985, UBUNTU-CVE-2019-3878

## What is CVE-2019-3878?

CVE-2019-3878 is a high-severity authentication bypass vulnerability in Canonical Ubuntu Linux, published on 26 Mar 2019. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A vulnerability was found in mod_auth_mellon before v0.14.2. If Apache is configured as a reverse proxy and mod_auth_mellon is configured to only let through authenticated users (with the require valid-user directive), adding special HTTP headers that are normally used to start the special SAML ECP (non-browser based) can be used to bypass authentication.

Weakness: CWE-287 (Improper Authentication), CWE-305 (Authentication Bypass by Primary Weakness)

## Which versions are affected by CVE-2019-3878?

It affects 10 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mod_auth_mellon` | Red Hat:enterprise_linux:8::appstream | All versions | 0:0.14.0-3.el8_0.2 |
| `mod_auth_mellon-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:0.14.0-3.el8_0.2 |
| `mod_auth_mellon-debugsource` | Red Hat:enterprise_linux:8::appstream | All versions | 0:0.14.0-3.el8_0.2 |
| `mod_auth_mellon-diagnostics-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:0.14.0-3.el8_0.2 |

Products: Canonical Ubuntu Linux, Fedoraproject Fedora, Mod Auth Mellon Project Mod Auth Mellon, Redhat Enterprise Linux, Redhat Enterprise Linux Desktop, Redhat Enterprise Linux Server, Redhat Enterprise Linux Server Aus, Redhat Enterprise Linux Server Eus, Redhat Enterprise Linux Server Tus, Redhat Enterprise Linux Workstation.

## How do I fix CVE-2019-3878?

Upgrade to a fixed version.

## Is CVE-2019-3878 being exploited?

There is no known exploitation of CVE-2019-3878 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-3878 and fix it if it is affected.

What it is: CVE-2019-3878 is a high-severity authentication bypass vulnerability in Canonical Ubuntu Linux, published on 26 Mar 2019. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2019-3878 in the wild and no public exploit code.

Affected product: Canonical Ubuntu Linux. 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-2019-3878/ (Markdown: https://insights.sbomify.com/CVE-2019-3878/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-3878
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-3878
- OSV: https://osv.dev/vulnerability/CVE-2019-3878

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-3878/
Summaries are generated and may contain mistakes; the official description above is the record.