CVE-2026-0966

Libssh: libssh: denial of service via zero-length input in ssh_get_hexa()

Published Mar 26, 2026 CVSS 3.1 · 8.2 High EPSS < 1% KEV · Not listed
Description
A flaw was found in libssh. The API function `ssh_get_hexa()` is vulnerable to a denial of service when processing zero-length input. This can be exploited remotely by an attacker during GSSAPI (Generic Security Service Application Program Interface) authentication if the server's logging verbosity is set to `SSH_LOG_PACKET (3)` or higher. Successful exploitation could lead to a self-Denial of Service of the per-connection daemon process.

Remediation

Vendor Workaround

Applications using libssh should avoid passing zero-length input to ssh_get_hexa(), ssh_get_fingerprint_hash(), and ssh_print_hexa(). For the remotely reachable GSSAPI authentication path, disable GSSAPI authentication in the affected libssh-based application if it is not required, or configure that application's libssh logging verbosity below SSH_LOG_PACKET (3). These measures address the GSSAPI logging path; they do not prevent other callers from passing zero-length input to the affected functions. Configuration and any required restart depend on the application using libssh. Changing the host's OpenSSH sshd_config or restarting the OpenSSH sshd service is not a general mitigation for applications using libssh. Apply the relevant vendor update containing the fix. Upstream fixed this issue in libssh 0.11.4 and 0.12.0; distribution packages may include a backported fix.

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4844-1 libssh security update
Debian DSA Debian DSA DSA-6410-1 libssh security update
Ubuntu USN Ubuntu USN USN-8051-2 libssh vulnerabilities
Ubuntu USN Ubuntu USN USN-8051-1 libssh vulnerabilities
History
Type Values Removed Values Added
First Time appeared Redhat rhel Els
CPEs cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/a:redhat:enterprise_linux:8
cpe:/o:redhat:rhel_els:6
cpe:/o:redhat:rhel_els:7
Vendors & Products Redhat rhel Els
Type Values Removed Values Added
CPEs cpe:/o:redhat:enterprise_linux:9 cpe:/a:redhat:enterprise_linux:9::appstream
cpe:/o:redhat:enterprise_linux:9::baseos
References
Type Values Removed Values Added
CPEs cpe:/o:redhat:enterprise_linux:10 cpe:/o:redhat:enterprise_linux:10.2
References
Type Values Removed Values Added
Description The API function `ssh_get_hexa()` is vulnerable, when 0-lenght input is provided to this function. This function is used internally in `ssh_get_fingerprint_hash()` and `ssh_print_hexa()` (deprecated), which is vulnerable to the same input (length is provided by the calling application). The function is also used internally in the gssapi code for logging the OIDs received by the server during GSSAPI authentication. This could be triggered remotely, when the server allows GSSAPI authentication and logging verbosity is set at least to SSH_LOG_PACKET (3). This could cause self-DoS of the per-connection daemon process. A flaw was found in libssh. The API function `ssh_get_hexa()` is vulnerable to a denial of service when processing zero-length input. This can be exploited remotely by an attacker during GSSAPI (Generic Security Service Application Program Interface) authentication if the server's logging verbosity is set to `SSH_LOG_PACKET (3)` or higher. Successful exploitation could lead to a self-Denial of Service of the per-connection daemon process.
Title Libssh: buffer underflow in ssh_get_hexa() on invalid input Libssh: libssh: denial of service via zero-length input in ssh_get_hexa()
Metrics cvssV3_0

{'score': 6.5, 'vector': 'CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L'}

cvssV3_0

{'score': 6.5, 'vector': 'CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H'}

Type Values Removed Values Added
First Time appeared Redhat hardened Images
Redhat openshift Container Platform
CPEs cpe:2.3:a:libssh:libssh:*:*:*:*:*:*:*:*
cpe:2.3:a:redhat:hardened_images:-:*:*:*:*:*:*:*
cpe:2.3:a:redhat:openshift_container_platform:4.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:*
Vendors & Products Redhat hardened Images
Redhat openshift Container Platform
Metrics cvssV3_1

{'score': 8.2, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H'}

Type Values Removed Values Added
First Time appeared Redhat hummingbird
CPEs cpe:/a:redhat:hummingbird:1
Vendors & Products Redhat hummingbird
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description No description is available for this CVE. The API function `ssh_get_hexa()` is vulnerable, when 0-lenght input is provided to this function. This function is used internally in `ssh_get_fingerprint_hash()` and `ssh_print_hexa()` (deprecated), which is vulnerable to the same input (length is provided by the calling application). The function is also used internally in the gssapi code for logging the OIDs received by the server during GSSAPI authentication. This could be triggered remotely, when the server allows GSSAPI authentication and logging verbosity is set at least to SSH_LOG_PACKET (3). This could cause self-DoS of the per-connection daemon process.
Title libssh: Buffer underflow in ssh_get_hexa() on invalid input Libssh: buffer underflow in ssh_get_hexa() on invalid input
First Time appeared Redhat
Redhat enterprise Linux
Redhat openshift
Weaknesses CWE-124
CPEs cpe:/a:redhat:openshift:4
cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat enterprise Linux
Redhat openshift
References
Metrics cvssV3_0

{'score': 6.5, 'vector': 'CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L'}

Type Values Removed Values Added
First Time appeared Libssh
Libssh libssh
Vendors & Products Libssh
Libssh libssh
Type Values Removed Values Added
Description No description is available for this CVE.
Title libssh: Buffer underflow in ssh_get_hexa() on invalid input
References
Metrics threat_severity

None

threat_severity

Moderate

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Nov 5, 2026, 4:11 PM
Reserved
Jan 14, 2026, 9:54 PM
Status
Modified
Published
Mar 26, 2026, 9:17 PM
Modified
Nov 5, 2026, 5:17 PM
Severity
Moderate
Public date
Feb 10, 2026, 6:47 PM