CVE-2018-15919
Description
A vulnerability was found in OpenSSH Server, where failed GSSAPI authentication attempts elicit different responses depending on whether the target username exists, a remote attacker could exploit this behavior to enumerate valid usernames on a system, potentially aiding in further attacks. This issue could be leveraged in reconnaissance efforts to identify existing user accounts.
Statement
This vulnerability is rated as moderate because OpenSSH Server responds differently to failed GSSAPI authentication attempts based on whether a target username exists, while this does not directly compromise system integrity, it could facilitate further attacks such as brute-force or credential-stuffing attempts.
Mitigation
If GSSAPI Authentication is not required, this flaw can be mitigated by changing the global configuration in `/etc/ssh/sshd_config` from `GSSAPIAuthentication yes` to `GSSAPIAuthentication no`.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.3 | 5.3 | 5.3 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | Low | Low | Low |
| Integrity Impact | None | None | None |
| Availability Impact | None | None | None |
Vector
Red Hat: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
NVD: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
