CVE intelligenceCISA KEV

CVE-2026-123158

OpenBSD OpenSSH Unexpected Status Code or Return Value Vulnerability

Published Nov 5, 2026Sources checked Nov 10, 2026

8.1HIGHCVSS out of 10

What this means

Actively exploited

CISA lists CVE-2026-123158 in its Known Exploited Vulnerabilities catalog, which means exploitation has been observed. The entry applies to OpenBSD OpenSSH.

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Nov 9, 2026

Release Notes

CISA KEVListedObserved exploitation

EPSS1.0%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-123158?

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.

Source: NVD

CISA says:Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.CISA catalog due date Nov 12, 2026