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libssh CVE-2026-59851

| EUVDEUVD-2026-46268 HIGH
Incorrect Authorization (CWE-863)
2026-07-21 redhat GHSA-x5cr-v39m-53gw
8.8
CVSS 3.1 · Vendor: redhat
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Severity by source

Vendor (redhat) PRIMARY
8.8 HIGH
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
8.8 HIGH

Network-reachable and low-complexity once authenticated (AV:N/AC:L); a valid Kerberos principal is required (PR:L); logging in as arbitrary users yields full C:H/I:H/A:H on the host with no scope change.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
SUSE
HIGH
qualitative
Red Hat
8.8 HIGH
qualitative

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Analysis Generated
Jul 21, 2026 - 15:02 vuln.today
CVE Published
Jul 21, 2026 - 14:20 cve.org
HIGH 8.8

DescriptionCVE.org

A flaw was found in libssh. On servers with GSSAPIKeyExchange enabled, the gssapi-keyex path does not verify whether the authenticated Kerberos principal is authorized for the requested local user, allowing authenticated clients to log in as arbitrary users.

AnalysisAI

Privilege escalation via authentication bypass in libssh affects servers that enable GSSAPIKeyExchange, where the gssapi-keyex authentication path fails to confirm that the authenticated Kerberos principal is actually authorized for the local user account being requested. An already-authenticated client holding any valid Kerberos principal in the realm can therefore log in as an arbitrary user, including potentially privileged accounts, on Red Hat Enterprise Linux 8, 9, and 10 and Red Hat Hardened Images. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Obtain valid Kerberos principal in realm
Delivery
Connect to libssh server with GSSAPIKeyExchange enabled
Exploit
Request login as arbitrary target user via gssapi-keyex
Execution
Server skips principal-to-user authorization check
Persist
Authenticate as impersonated privileged account
Impact
Full host compromise

Vulnerability AssessmentAI

Exploitation Exploitation requires the target SSH server to be built on libssh and explicitly configured with GSSAPIKeyExchange enabled (the vulnerable gssapi-keyex authentication path), which is not the default configuration. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The signals point to a genuine, actionable priority in Kerberos/GSSAPI-enabled environments, but with an important scoping caveat. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker who holds any valid Kerberos principal in the realm (for example a low-privileged domain user or a compromised service account) connects over the network to a libssh-based SSH server that has GSSAPIKeyExchange enabled and completes gssapi-keyex authentication while requesting a different, higher-value local username such as root or an application service account. Because the server never checks that their principal is authorized for that account, the login succeeds and they obtain that user's shell and privileges. …
Remediation Apply the Red Hat libssh security update for your RHEL 8, 9, or 10 release or Red Hat Hardened Image; exact fixed version numbers are not included in the provided data, so obtain them from the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-59851 and the Bugzilla tracker at https://bugzilla.redhat.com/show_bug.cgi?id=2498184 rather than assuming a version. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, audit all RHEL 8, 9, and 10 systems to identify those running libssh with GSSAPIKeyExchange enabled and document their role, criticality, and current user population. …

Sign in for detailed remediation steps and compensating controls.

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise Micro 5.3 Affected
SUSE Linux Enterprise Micro 5.4 Affected
SUSE Linux Enterprise Micro 5.5 Affected

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CVE-2026-59851 vulnerability details – vuln.today

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