---
title: "CVE-2018-12556\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2018-12556?format=md
keywords: index, follow
---

# CVE-2018-12556

Publication date 16 May 2019

Last updated 11 July 2025

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**5.9 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2018-12556?format=md#impact-score)

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## Description

The signature verification routine in install.sh in yarnpkg/website through
2018-06-05 only verifies that the yarn release is signed by any (arbitrary)
key in the local keyring of the user, and does not pin the signature to the
yarn release key, which allows remote attackers to sign tampered yarn
release packages with their own key.

[Read the notes from the security team](https://ubuntu.com/security/CVE-2018-12556?format=md#notes)

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| node-yarnpkg | 26.04 LTS resolute | Needs evaluation |
| 25.10 questing | Ignored end of life, was needs-triage |
| 25.04 plucky | Ignored end of life, was needs-triage |
| 24.10 oracular | Ignored end of life, was needs-triage |
| 24.04 LTS noble | Needs evaluation |
| 23.10 mantic | Ignored end of life, was needs-triage |
| 23.04 lunar | Ignored end of life, was needs-triage |
| 22.10 kinetic | Ignored end of life, was needs-triage |
| 22.04 LTS jammy | Needs evaluation |
| 21.10 impish | Ignored end of life |
| 21.04 hirsute | Ignored end of life |
| 20.10 groovy | Ignored end of life |
| 20.04 LTS focal | Needs evaluation |
| 19.10 eoan | Ignored end of life |
| 19.04 disco | Ignored end of life |
| 18.10 cosmic | Not in release |
| 18.04 LTS bionic | Not in release |
| 16.04 LTS xenial | Not in release |
| 14.04 LTS trusty | Not in release |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Notes

---

### [seth-arnold](https://launchpad.net/~seth-arnold)

It appears this is about the install.sh that is run via a
curl url | bash - auto-updated mechanism inside the program. It looks
like it tries to determine if it was installed via deb and if so, runs:
sudo apt-get update && sudo apt-get install yarn
So it's possible the unsafe mechanism isn't used in our packages.
It's also possible this is seriously unsafe.

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

5.9 · Medium

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | High |
  | Privileges required | None |
  | User interaction | None |
  | Scope | Unchanged |
  | Confidentiality impact | None |
  | Integrity impact | High |
  | Availability impact | None |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 5.9 · Medium |
  | Exploitability score | - |
  | Impact score | - |

**Vector:** CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-12556)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2018-12556)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2018-12556)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2018-12556)

### Other references

* <http://packetstormsecurity.com/files/152703/Johnny-You-Are-Fired.html>
* <http://seclists.org/fulldisclosure/2019/Apr/38>
* <https://github.com/RUB-NDS/Johnny-You-Are-Fired>
* <https://github.com/RUB-NDS/Johnny-You-Are-Fired/blob/master/paper/johnny-fired.pdf>
* <https://github.com/yarnpkg/website/commits/master>
* <https://www.openwall.com/lists/oss-security/2019/04/30/4>
* <https://neopg.io/blog/yarn-signature-bypass/>
* <https://www.cve.org/CVERecord?id=CVE-2018-12556>