CVE-2026-59849

Libssh: libssh: denial of service via automatic certificate authentication loop

Published Jul 21, 2026 CVSS 3.1 · 3.1 Low EPSS < 1% KEV · Not listed
Description
A flaw was found in libssh. Logic errors in automatic certificate-based public key authentication can cause libssh clients to loop indefinitely when configured certificates are missing or repeatedly rejected by a server, leading to denial of service.

Remediation

Vendor Workaround

Do not connect to untrusted SSH servers and do not use certificates until patched.

Tracking

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Advisories

Source ID Title
Debian DSA Debian DSA DSA-6410-1 libssh security update
Ubuntu USN Ubuntu USN USN-8699-1 libssh vulnerabilities
History
Type Values Removed Values Added
CPEs cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
cpe:/a:redhat:enterprise_linux:8
cpe:/a:redhat:enterprise_linux:9
Type Values Removed Values Added
First Time appeared Redhat enterprise Linux For Els
Redhat enterprise Linux For Eus
Redhat enterprise Linux For Ibm Z Systems
Redhat enterprise Linux For Ibm Z Systems Els
Redhat enterprise Linux For Ibm Z Systems Eus
Redhat enterprise Linux For Power Little Endian
Redhat enterprise Linux For Power Little Endian Els
Redhat enterprise Linux For Power Little Endian Eus
CPEs cpe:2.3:a:libssh:libssh:-:*:*:*:*:*:*:* cpe:2.3:a:libssh:libssh:*:*:*:*:*:*:*:*
cpe:2.3:a:libssh:libssh:0.12.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux:10.0:*:*:*:*:*:arm64:*
cpe:2.3:o:redhat:enterprise_linux:10.0:*:*:*:*:*:x64:*
cpe:2.3:o:redhat:enterprise_linux:10.2:*:*:*:*:*:arm64:*
cpe:2.3:o:redhat:enterprise_linux:10.2:*:*:*:*:*:x64:*
cpe:2.3:o:redhat:enterprise_linux_for_els:10.2:*:*:*:*:*:arm64:*
cpe:2.3:o:redhat:enterprise_linux_for_els:10.2:*:*:*:*:*:x64:*
cpe:2.3:o:redhat:enterprise_linux_for_eus:10.2:*:*:*:*:*:arm64:*
cpe:2.3:o:redhat:enterprise_linux_for_eus:10.2:*:*:*:*:*:x64:*
cpe:2.3:o:redhat:enterprise_linux_for_ibm_z_systems:10.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_for_ibm_z_systems:10.2:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_for_ibm_z_systems_els:10.2:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_for_ibm_z_systems_eus:10.2:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_for_power_little_endian:10.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_for_power_little_endian:10.2:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_for_power_little_endian_els:10.2:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_for_power_little_endian_eus:10.2:*:*:*:*:*:*:*
Vendors & Products Redhat enterprise Linux For Els
Redhat enterprise Linux For Eus
Redhat enterprise Linux For Ibm Z Systems
Redhat enterprise Linux For Ibm Z Systems Els
Redhat enterprise Linux For Ibm Z Systems Eus
Redhat enterprise Linux For Power Little Endian
Redhat enterprise Linux For Power Little Endian Els
Redhat enterprise Linux For Power Little Endian Eus
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
First Time appeared Libssh
Libssh libssh
Redhat hardened Images
Vendors & Products Libssh
Libssh libssh
Redhat hardened Images
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description A flaw was found in libssh. Logic errors in automatic certificate-based public key authentication can cause libssh clients to loop indefinitely when configured certificates are missing or repeatedly rejected by a server, leading to denial of service.
Title Libssh: libssh: denial of service via automatic certificate authentication loop
First Time appeared Redhat
Redhat enterprise Linux
Redhat hummingbird
Weaknesses CWE-835
CPEs cpe:/a:redhat:hummingbird:1
cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat enterprise Linux
Redhat hummingbird
References
Metrics cvssV3_1

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