CyberSecBulletin
CVE-2026-123158Exploited in the wildNVD status: Analyzed

OpenBSD OpenSSH Unexpected Status Code or Return Value

Published Updated By the CyberSecBulletin desk

CVE-2026-123158 is a high-severity unexpected status code or return value vulnerability in OpenSSH from OpenBSD, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 10.6p2 as the first without the flaw, so updating OpenSSH to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on November 9, 2026, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update OpenSSH to 10.6p2 or a later version.
  2. CISA's required action: 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.
  3. Read the advisory on marc.info for workarounds and exact fixed builds.
  4. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
OpenBSDOpenSSHbefore 10.6p210.6p2

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
HighSuccess depends on conditions outside the attacker's control.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (mitre.org).

Official description

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: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Unexpected Status Code or Return Value

The product does not properly check when a function or operation returns a value that is legitimate for the function, but is not expected by the product.

More Unexpected Status Code or Return Value vulnerabilities (CWE-394)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
  3. Added to CISA's Known Exploited Vulnerabilities catalogue.
  4. Record last changed materially (score, affected products, status or references).
  5. Deadline for US federal agencies to remediate, set by CISA.

References

Technical write-ups (may include proof of concept)

Our coverage

Other vulnerabilities in OpenSSH

All OpenSSH vulnerabilities

Recent Unexpected Status Code or Return Value vulnerabilities

Spotted an error? Tell us.