CVE-2026-123158: CVE-2026-123158: sshd in OpenSSH before 10.6p2 on Linux, when musl libc is used without PAM, lacks a workar…

CVE-2026-123158 at a glance

CVE-2026-123158 is a high-severity Auth Bypass vulnerability in the affected product, with a CVSS 3.1 base score of 8.1. NVD published it on 2026-11-05 and classifies the weakness as CWE-394. Public exploit code: 9 public GitHub proof-of-concept repositories from 9 accounts, with the earliest exploit evidence dated 2026-11-05. NVD does not list a fixed version, so the vendor advisory is the reference for the fix. CVERadar maps 1 MITRE ATT&CK technique across Stealth, Persistence, Privilege Escalation and Initial Access, inferred from the CWE and the description. Its CVERadar threat level is 45/100.

What it is

sshd in OpenSSH before 10.6p2 on Linux, when musl libc is used without PAM, lacks a workaround for a password authentication bypass (related to misinterpretation of whether a string is intended to be a password hash). For some configurations of accounts, any password between 256 and 1024 characters succeeds. An example of a platform using musl libc without PAM is Alpine Linux.

Exploitation evidence

First exploit evidence seen: 2026-11-05 (earliest date across the sources below).

Exploited in the wild

No source on this site lists in-the-wild exploitation yet (CISA KEV, VulnCheck KEV).

Public exploit code

GitHub proof-of-concept repositories

9 public repositories from 9 accounts, first seen 2026-11-05. Most starred: 0xBlackash/CVE-2026-123158 (1 stars), view the 0xBlackash/CVE-2026-123158 repository on GitHub.

Verify before running: public PoCs can be malicious. Read the code and only run it in an isolated lab. A PoC means exploit code is public, not that this CVE is exploited in the wild.

Sources: nomi-sec/PoC-in-GitHub.

Patches, mitigations and detection

Fixed versions

NVD does not list a fixed version for this CVE. Use the vendor advisory below.

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

No vendor-tagged reference yet; see the full reference list.

MITRE ATT&CK mitigations for this chain

• M1027 Password Policies (for T1078) : Applications and appliances that utilize default username and password should be changed immediately after the installation, and before deployment to a production environment. When possible, applications that use SSH keys should be updated periodically and properly secured. Policies should minimize (if not eliminate)
• M1018 User Account Management (for T1078) : Regularly audit user accounts for activity and deactivate or remove any that are no longer needed.
• M1026 Privileged Account Management (for T1078) : Audit domain and local accounts as well as their permission levels routinely to look for situations that could allow an adversary to gain wide access by obtaining credentials of a privileged account. These audits should also include if default accounts have been enabled, or if new local accounts are created that have
• M1032 Multi-factor Authentication (for T1078) : Implement multi-factor authentication (MFA) across all account types, including default, local, domain, and cloud accounts, to prevent unauthorized access, even if credentials are compromised. MFA provides a critical layer of security by requiring multiple forms of verification beyond just a password. This measure sign
• M1013 Application Developer Guidance (for T1078) : Ensure that applications do not store sensitive data or credentials insecurely. (e.g. plaintext credentials in code, published credentials in repositories, or credentials in public cloud storage).
• M1017 User Training (for T1078) : Applications may send push notifications to verify a login as a form of multi-factor authentication (MFA). Train users to only accept valid push notifications and to report suspicious push notifications.
• M1015 Active Directory Configuration (for T1078) : Disable legacy authentication, which does not support MFA, and require the use of modern authentication protocols instead.
• M1036 Account Use Policies (for T1078) : Use conditional access policies to block logins from non-compliant devices or from outside defined organization IP ranges.

Detection Generic guidance

• Initial Access: Alert on unusual requests to the affected service (odd paths, oversized payloads, exploit strings) in WAF, reverse-proxy and application logs.
• Persistence: Look for new files in web roots, new scheduled tasks/services, and new accounts created after the exposure window.
• Privilege Escalation: Alert on processes gaining SYSTEM/root unexpectedly, and on exploitation crashes of privileged services.

Response checklist Generic guidance

1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.

Hypervisors and Linux hosts need scheduled maintenance windows; managed server support from LayerLogix can plan and run them.