# CVE-2019-14870: Auth bypass in samba

> Samba AD DC fails to enforce non-forwardable ticket restrictions for S4U2Self, allowing attackers to bypass delegation constraints and potentially escalate privileges.

- **Severity:** Medium 5.4 (`CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/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:** 10 Dec 2019
- **Updated:** 5 Aug 2024
- **Also known as:** ALPINE-CVE-2019-14870, CLEANSTART-2024-NY89465, DEBIAN-CVE-2019-14870, ECHO-6f51-4099-25c6, GHSA-6q5r-wx7g-rq28, UBUNTU-CVE-2019-14870

## What is CVE-2019-14870?

CVE-2019-14870 is a medium-severity authentication bypass vulnerability in Canonical Ubuntu Linux, published on 10 Dec 2019. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

All Samba versions 4.x.x before 4.9.17, 4.10.x before 4.10.11 and 4.11.x before 4.11.3 have an issue, where the S4U (MS-SFU) Kerberos delegation model includes a feature allowing for a subset of clients to be opted out of constrained delegation in any way, either S4U2Self or regular Kerberos authentication, by forcing all tickets for these clients to be non-forwardable. In AD this is implemented by a user attribute delegation_not_allowed (aka not-delegated), which translates to disallow-forwardable. However the Samba AD DC does not do that for S4U2Self and does set the forwardable flag even if the impersonated client has the not-delegated flag set.

Weakness: CWE-287 (Improper Authentication), CWE-285 (Improper Authorization)

## Which versions are affected by CVE-2019-14870?

It affects 5 products.


Products: Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora, Opensuse Leap, Samba Samba.

## How do I fix CVE-2019-14870?

Upgrade to a fixed version.

## Is CVE-2019-14870 being exploited?

There is no known exploitation of CVE-2019-14870 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-2019-14870 and fix it if it is affected.

What it is: CVE-2019-14870 is a medium-severity authentication bypass vulnerability in Canonical Ubuntu Linux, published on 10 Dec 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-2019-14870 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-2019-14870/ (Markdown: https://insights.sbomify.com/CVE-2019-14870/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-14870
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-14870
- OSV: https://osv.dev/vulnerability/CVE-2019-14870

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From sbomify Insights: https://insights.sbomify.com/CVE-2019-14870/
Summaries are generated and may contain mistakes; the official description above is the record.