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Full vulnerability report · 2026
CVE-2026-123158High confidence

OpenBSD OpenSSH Unexpected Status Code or Return Value Vulnerability

OpenBSD · OpenSSH

8.1HighCVSS 3.1
Recommended action
Patch now

CISA confirms exploitation in the wild and lists 2026-11-12 as the remediation due date.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 9 Nov 2026

Evidence used

  • CISA confirms exploitation in the wild.
  • A structured source references public exploit or proof-of-concept material.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 18.90% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs OpenBSD OpenSSH and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-123158 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityopenssh: OpenSSH: Password authentication bypass via password hash misinterpretation
39 known not affected

The vendor explicitly states that these products are not affected by this CVE.

  • openssh.src as a component of Red Hat Enterprise Linux 10
  • openssh as a component of Red Hat Enterprise Linux 6
  • openssh-askpass as a component of Red Hat Enterprise Linux 6
  • openssh-clients as a component of Red Hat Enterprise Linux 6
  • openssh-ldap as a component of Red Hat Enterprise Linux 6
  • openssh-server as a component of Red Hat Enterprise Linux 6
  • openssh.src as a component of Red Hat Enterprise Linux 6
  • pam_ssh_agent_auth as a component of Red Hat Enterprise Linux 6
  • openssh as a component of Red Hat Enterprise Linux 7
  • openssh-askpass as a component of Red Hat Enterprise Linux 7
  • openssh-cavs as a component of Red Hat Enterprise Linux 7
  • openssh-clients as a component of Red Hat Enterprise Linux 7
Summary
A flaw was found in OpenSSH. When running on Linux systems utilizing the musl standard C library without Pluggable Authentication Modules (PAM), the SSH server can misinterpret input strings as password hashes. A remote, unauthenticated attacker can exploit this flaw by submitting a specially sized password, bypassing password authentication and gaining unauthorized access to affected accounts.
Remediation
No remediation text is recorded.
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Recommended actionPatch now

CISA confirms exploitation in the wild and lists 2026-11-12 as the remediation due date.

Patch available
01

What, why and how

OpenBSD OpenSSH on Linux contains an unexpected status code or return value vulnerability that could allow for authentication bypass.

What

OpenBSD OpenSSH on Linux contains an unexpected status code or return value vulnerability that could allow for authentication bypass.

Why

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.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may bypass an access boundary or take over an account.

What

OpenBSD OpenSSH on Linux contains an unexpected status code or return value vulnerability that could allow for authentication bypass.

Why

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.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may bypass an access boundary or take over an account.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Confirmed in the wild

CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2026-11-09.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
a network path → Unexpected Status Code or Return Value → bypass an access boundary or take over an account
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
High: exploitation depends on specific conditions
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-394 ↗

CWE-394: 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.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
Stolen credentials, tokens and legitimate administration functions may provide continued access without deploying a large custom toolset.
NetworkUnauthenticatedCWE-394CISA KEVPublic exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2026-4365OpenSSH: Schwachstelle ermöglicht Erlangen von Administratorrechten

Ein entfernter, anonymer Angreifer kann eine Schwachstelle in OpenSSH (in Kombination mit musl libc und ohne PAM) ausnutzen, um Administratorrechte zu erlangen.

Official advisory ↗
Canadian Centre for Cyber Security · English · AV26-1130OpenBSD security advisory (AV26-1130) - Update 1

As of November 5, 2026, OpenBSD is affected by a vulnerability in the following product: On November 9, 2026, Cybersecurity and Infrastructure Security Agency (CISA) added CVE-2026-123158 to their Known Exploited Vulnerabilities (KEV) Catalog

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20261111Security Bulletin 11 Nov 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 11 Nov 2026, published on 11 November 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
INCIBE-CERT · Spanish · omision-de-autenticacion-por-contrasena-en-openssh-de-alpine-linuxOmisión de autenticación por contraseña en OpenSSH de Alpine Linux

Özgün Kültekin, de Wakefield, ha informado sobre una vulnerabilidad de severidad alta. Un atacante podría iniciar sesión en cuentas sin contraseña configurada en los sistemas afectados.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-1468Avis du CERT-FR

Une vulnérabilité a été découverte dans OpenSSH. Elle permet à un attaquant de provoquer un contournement de la politique de sécurité.

Official advisory ↗
NBSZ-NKI · Hungarian · cve-2026-123158CVE-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.

Official advisory ↗
CSIRT Italia · Italian · openssh-potenziale-bypass-dell-autenticazione-su-sistemi-linux-basati-su-musl-libcOpenSSH: potenziale bypass dell'autenticazione su sistemi Linux basati su musl libc

È stata recentemente sanata una vulnerabilità con gravità “alta” nel servizio OpenSSH Server (sshd), dovuta a un'errata gestione della verifica delle credenziali nei sistemi Linux che utilizzano la libreria musl libc con il modulo di autenticazione PAM disabilitato. Nel dettaglio, la vulnerabilità denominata "SSHole" e identificata tramite la CVE-2026-123158 - di tipo " Authentication Bypass " e con score CVSS 3.1 pari a 8.1 - è dovuta ad un'errata gestione del valore restituito dalla funzione crypt() di musl libc, che utilizza il carattere “*” per segnalare un eventuale errore durante l'elaborazione di password con dimensioni superiori a 256 byte. Tale carattere può coincidere con quello utilizzato dal sistema per identificare gli account per i quali l'accesso tramite password è disabilitato. In queste condizioni, OpenSSH potrebbe interpretare erroneamente la corrispondenza come una verifica riuscita, consentendo a un attaccante di aggirare i controlli di autenticazione. Un attaccante remoto non autenticato potrebbe sfruttare tale vulnerabilità, inviando richieste di autenticazione SSH contenenti password opportunamente predisposte, di lunghezza compresa tra 257 e 1.024 byte, per accedere senza autorizzazione ai sistemi interessati. Qualora l'account utilizzato disponga di privilegi elevati, o consenta di acquisirli, l'attaccante potrebbe ottenere il controllo completo del sistema. Lo sfruttamento richiede l'abilitazione dell'autenticazione SSH tramite password e la presenza, sul sistema, di almeno un account per il quale l'accesso tramite password è disabilitato e di un altro account le cui credenziali sono memorizzate sotto forma di hash SHA-256 crypt o SHA-512 crypt.

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-7058美 CISA 발표 주요 Exploit 정보공유(Update. 2026-11-09)

OpenBSD OpenSSH Unexpected Status Code or Return Value Vulnerability

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-7055OpenSSH 보안 업데이트 권고

OpenSSH에서 비밀번호 처리 오류로 인해 발생하는 인증 우회 취약점(CVE-2026-123158)

Official advisory ↗
NCSC-NL · Dutch · NCSC-2026-0469Kwetsbaarheid verholpen in OpenSSH door OpenSSH Project

OpenSSH sshd versions prior to 10.6p2 on Linux systems using musl libc without PAM are vulnerable to a password authentication bypass for passwords between 256 and 1024 characters, notably impacting Alpine Linux.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
OpenSSH: < 10.6p2
Fixed
An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 5 Nov 2026 · Last source change 10 Nov 2026, 04:55 UTC · CWE-394 · Unexpected Status Code or Return Value

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-11-10
European sourceNo official EUVD mapping
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Vendor guidanceAuthoritative vendor guidance changed: added patch: github.com/4353fdc43ef646c43a8dda7025cc1a898caf1482; added remediation: github.com/4353fdc43ef646c43a8dda7025cc1a898caf1482; 1 further additions.
    Before
    no authoritative guidance recorded
    After
    patch: github.com/4353fdc43ef646c43a8dda7025cc1a898caf1482 · remediation: github.com/4353fdc43ef646c43a8dda7025cc1a898caf1482 · vendor advisory: marc.info?l=openssh-unix-dev&m=179388064263131&w=2
    cve@mitre.org ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    OpenSSH: < 10.6p2 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    OpenSSH: < 10.6p2 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  3. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    cve@mitre.org ↗
  4. Public exploit evidencePublic exploit evidence changed from No public exploit to Public exploit reference.
    Before
    No public exploit
    After
    Public exploit reference
    cve@mitre.org ↗
  5. Public exploit evidencePublic exploit evidence changed from Public exploit reference to No public exploit.
    Before
    Public exploit reference
    After
    No public exploit
    CVE.org ↗
  6. CISA KEV stateCISA KEV now confirms exploitation in the wild.
    Before
    not listed in CISA KEV
    After
    listed in CISA KEV since 2026-11-09
    CISA KEV ↗
  7. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Added to CISA KEV
Fixed release or patch reference recorded
Vendor CSAF · Red Hat Product Security↗CISA KEV record↗Patch or update reference↗Vendor advisory↗CVE authority or vendor reference↗Public exploit reference↗Public exploit reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-123158 · cve.blacktree.nl