openssh: User enumeration via malformed packets in authentication requests
Published Aug 28, 2018
5.3
MEDIUMCVSS 3.1
EPSS 3.56%
Description
Remotely observable behaviour in auth-gss2.c in OpenSSH through 7.8 could be used by remote attackers to detect existence of users on a target system when GSS2 is in use. NOTE: the discoverer states 'We understand that the OpenSSH developers do not want to treat such a username enumeration (or "oracle") as a vulnerability.'
Affected products
No data.
Configuration 2
- n/a
- n/a
- n/a
- n/a
Configuration 3
- n/a
No data.
Red Hat Enterprise Linux 5
openssh
Not affected
Red Hat Enterprise Linux 6
openssh
Not affected
Red Hat Enterprise Linux 7
openssh
Will not fix
Red Hat Enterprise Linux 8
openssh
Will not fix
Red Hat Virtualization 4
openssh
Will not fix
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 5 | openssh | Not affected | n/a |
| Red Hat Enterprise Linux 6 | openssh | Not affected | n/a |
| Red Hat Enterprise Linux 7 | openssh | Will not fix | n/a |
| Red Hat Enterprise Linux 8 | openssh | Will not fix | n/a |
| Red Hat Virtualization 4 | openssh | Will not fix | n/a |
No package ranges for this CVE.
Remediation
Red Hat 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.
Red Hat 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`.
Metrics
No CVSS v4.0 score for this CVE.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
AV:N/AC:L/Au:N/C:P/I:N/A:N
This CVE is not in the KEV list.
CISA SSVC (Vulnrichment)
Stakeholder-Specific Vulnerability Categorization from CISA ADP.
Exploitation
PoCAutomatable
YesTechnical Impact
PartialDecision
n/aAssessed Dec 18, 2025 · SSVC 2.0.3
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.
Score over time
2021–2026- EPSS v1
- EPSS v5
- EPSS v2
- EPSS v3
- EPSS v4
Percentile over time
- EPSS v1
- EPSS v5
- EPSS v2
- EPSS v3
- EPSS v4
Table of values (17 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 1, 2026 | 3.56% (0.03557) | 88.94th | v5 (v2026.06.15) |
| Jun 15, 2026 | 3.56% (0.03557) | 87.79th | v5 (v2026.06.15) |
| Dec 18, 2025 | 1.56% (0.01559) | 81.01th | v4 (v2025.03.14) |
| Aug 1, 2025 | 0.41% (0.00414) | 60.91th | v4 (v2025.03.14) |
| Mar 30, 2025 | 1.69% (0.01691) | 80.56th | v4 (v2025.03.14) |
| Mar 29, 2025 | 5.99% (0.05988) | 84.04th | v4 (v2025.03.14) |
| Mar 17, 2025 | 1.69% (0.01691) | 80.99th | v4 (v2025.03.14) |
| Dec 12, 2024 | 0.26% (0.00257) | 65.98th | v3 (v2023.03.01) |
| Feb 28, 2024 | 0.26% (0.00257) | 64.67th | v3 (v2023.03.01) |
| Jan 19, 2024 | 0.24% (0.00244) | 62.35th | v3 (v2023.03.01) |
| Sep 26, 2023 | 0.27% (0.00273) | 64.17th | v3 (v2023.03.01) |
| Sep 3, 2023 | 0.28% (0.00278) | 64.24th | v3 (v2023.03.01) |
| Mar 7, 2023 | 0.31% (0.00307) | 65.11th | v3 (v2023.03.01) |
| Mar 6, 2023 | 5.74% (0.05736) | 90.33th | v2 (v2022.01.01) |
| Feb 4, 2022 | 5.74% (0.05736) | 77.22th | v2 (v2022.01.01) |
| Feb 3, 2022 | 4.53% (0.04526) | 76.76th | v5 (v2026.06.15) |
| Apr 14, 2021 | 4.53% (0.04526) | 0.00th | v1 |
References (7)
- http://seclists.org/oss-sec/2018/q3/180 x_refsource_MISCMailing ListPatchThird Party Advisory
- http://www.securityfocus.com/bid/105163 vdb-entryx_refsource_BIDThird Party AdvisoryVDB Entry
- https://access.redhat.com/security/cve/CVE-2018-15919 Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1623184 Issue Tracking
- https://nvd.nist.gov/vuln/detail/CVE-2018-15919
- https://security.netapp.com/advisory/ntap-20181221-0001/ x_refsource_CONFIRMThird Party Advisory
- https://www.cve.org/CVERecord?id=CVE-2018-15919
| Link | Providers | Tags |
|---|---|---|
| http://seclists.org/oss-sec/2018/q3/180 | x_refsource_MISCMailing ListPatchThird Party Advisory | |
| http://www.securityfocus.com/bid/105163 | vdb-entryx_refsource_BIDThird Party AdvisoryVDB Entry | |
| https://access.redhat.com/security/cve/CVE-2018-15919 | Vendor Advisory | |
| https://bugzilla.redhat.com/show_bug.cgi?id=1623184 | Issue Tracking | |
| https://nvd.nist.gov/vuln/detail/CVE-2018-15919 | ||
| https://security.netapp.com/advisory/ntap-20181221-0001/ | x_refsource_CONFIRMThird Party Advisory | |
| https://www.cve.org/CVERecord?id=CVE-2018-15919 |
Change history (0)
No recorded changes yet.