# CVE-2018-15473: Information disclosure in n/a

> OpenSSH allows attackers to enumerate valid usernames due to a race condition in authentication packet parsing.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Aug 2018
- **Updated:** 17 Dec 2025
- **Also known as:** ALPINE-CVE-2018-15473, DEBIAN-CVE-2018-15473, DLA-1474-1, DSA-4280-1, GHSA-c8qw-h3f6-fv63, MGASA-2018-0363, RHSA-2019:0711, RHSA-2019:2143, SUSE-SU-2018:3686-1, SUSE-SU-2018:3768-1, SUSE-SU-2018:3776-1, SUSE-SU-2018:3776-2, SUSE-SU-2018:3781-1, SUSE-SU-2018:3910-1, UBUNTU-CVE-2018-15473, openSUSE-SU-2021:1383-1, openSUSE-SU-2021:1390-1, openSUSE-SU-2024:11407-1

## What is CVE-2018-15473?

CVE-2018-15473 is a medium-severity vulnerability in Canonical Ubuntu Linux, published on 17 Aug 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

OpenSSH through 7.7 is prone to a user enumeration vulnerability due to not delaying bailout for an invalid authenticating user until after the packet containing the request has been fully parsed, related to auth2-gss.c, auth2-hostbased.c, and auth2-pubkey.c.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2018-15473?

It affects 22 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `openssh` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-124.el6_10 |
| `openssh-askpass` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-124.el6_10 |
| `openssh-clients` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-124.el6_10 |
| `openssh-debuginfo` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-124.el6_10 |
| `openssh-ldap` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-124.el6_10 |
| `openssh-server` | Red Hat:enterprise_linux:6::client | All versions | 0:5.3p1-124.el6_10 |
| `pam_ssh_agent_auth` | Red Hat:enterprise_linux:6::client | All versions | 0:0.9.3-124.el6_10 |
| `openssh` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-124.el6_10 |
| `openssh-askpass` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-124.el6_10 |
| `openssh-clients` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-124.el6_10 |
| `openssh-debuginfo` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-124.el6_10 |
| `openssh-ldap` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-124.el6_10 |
| `openssh-server` | Red Hat:enterprise_linux:6::computenode | All versions | 0:5.3p1-124.el6_10 |
| `pam_ssh_agent_auth` | Red Hat:enterprise_linux:6::computenode | All versions | 0:0.9.3-124.el6_10 |
| `openssh` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-124.el6_10 |
| `openssh-askpass` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-124.el6_10 |
| `openssh-clients` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-124.el6_10 |
| `openssh-debuginfo` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-124.el6_10 |
| `openssh-ldap` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-124.el6_10 |
| `openssh-server` | Red Hat:enterprise_linux:6::server | All versions | 0:5.3p1-124.el6_10 |
| `pam_ssh_agent_auth` | Red Hat:enterprise_linux:6::server | All versions | 0:0.9.3-124.el6_10 |
| `openssh` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-124.el6_10 |
| `openssh-askpass` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-124.el6_10 |
| `openssh-clients` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-124.el6_10 |
| `openssh-debuginfo` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-124.el6_10 |
| `openssh-ldap` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-124.el6_10 |
| `openssh-server` | Red Hat:enterprise_linux:6::workstation | All versions | 0:5.3p1-124.el6_10 |
| `pam_ssh_agent_auth` | Red Hat:enterprise_linux:6::workstation | All versions | 0:0.9.3-124.el6_10 |
| `openssh` | Red Hat:enterprise_linux:7::client | All versions | 0:7.4p1-21.el7 |
| `openssh-askpass` | Red Hat:enterprise_linux:7::client | All versions | 0:7.4p1-21.el7 |
| `openssh-cavs` | Red Hat:enterprise_linux:7::client | All versions | 0:7.4p1-21.el7 |
| `openssh-clients` | Red Hat:enterprise_linux:7::client | All versions | 0:7.4p1-21.el7 |
| `openssh-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:7.4p1-21.el7 |
| `openssh-keycat` | Red Hat:enterprise_linux:7::client | All versions | 0:7.4p1-21.el7 |
| `openssh-ldap` | Red Hat:enterprise_linux:7::client | All versions | 0:7.4p1-21.el7 |
| `openssh-server` | Red Hat:enterprise_linux:7::client | All versions | 0:7.4p1-21.el7 |
| `openssh-server-sysvinit` | Red Hat:enterprise_linux:7::client | All versions | 0:7.4p1-21.el7 |
| `pam_ssh_agent_auth` | Red Hat:enterprise_linux:7::client | All versions | 0:0.10.3-2.21.el7 |
| `openssh` | Red Hat:enterprise_linux:7::computenode | All versions | 0:7.4p1-21.el7 |
| `openssh-askpass` | Red Hat:enterprise_linux:7::computenode | All versions | 0:7.4p1-21.el7 |

Products: Canonical Ubuntu Linux, Debian Debian Linux, Netapp Aff Baseboard Management Controller, Netapp Cloud Backup, Netapp Clustered Data Ontap, Netapp Cn1610 Firmware, Netapp Data Ontap, Netapp Data Ontap Edge, Netapp Fas Baseboard Management Controller, Netapp Oncommand Unified Manager, Netapp Ontap Select Deploy, Netapp Service Processor, Netapp Steelstore Cloud Integrated Storage, Netapp Storage Replication Adapter, Netapp Vasa Provider, Netapp Virtual Storage Console, OpenSSH, Oracle Sun Zfs Storage Appliance Kit, Redhat Enterprise Linux Desktop, Redhat Enterprise Linux Server and 2 more.

## How do I fix CVE-2018-15473?

Apply the vendor's patch.

## Is CVE-2018-15473 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2018-15473 exists.

Public exploit code:

- Exploit written in Python for CVE-2018-15473 with threading and export formats (github_poc): https://github.com/Rhynorater/CVE-2018-15473-Exploit
- OpenSSH 2.3 up to 7.4 Mass Username Enumeration (CVE-2018-15473). (github_poc): https://github.com/trimstray/massh-enum
- Multi-threaded, IPv6 aware, wordlists/single-user username enumeration via CVE-2018-15473 (github_poc): https://github.com/epi052/cve-2018-15473
- OpenSSH 2.3 < 7.7 - Username Enumeration (github_poc): https://github.com/Sait-Nuri/CVE-2018-15473
- OpenSSH 7.7 - Username Enumeration (github_poc): https://github.com/r3dxpl0it/CVE-2018-15473
- SSH User Enumerator in Python3, CVE-2018-15473, I updated the code of this exploit (https://www.exploit-db.com/exploits/45939) to work with python3 instead of python2. (github_poc): https://github.com/sergiovks/SSH-User-Enum-Python3-CVE-2018-15473

## 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-2018-15473 and fix it if it is affected.

What it is: CVE-2018-15473 is a medium-severity vulnerability in Canonical Ubuntu Linux, published on 17 Aug 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2018-15473 exists.

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-2018-15473/ (Markdown: https://insights.sbomify.com/CVE-2018-15473/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-15473
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-15473
- OSV: https://osv.dev/vulnerability/CVE-2018-15473

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-15473/
Summaries are generated and may contain mistakes; the official description above is the record.