CVE-2026-45156

Status: DeferredHigh (8.1)—

Nextcloud is an open source content collaboration platform. From versions 0.3.0 to before 3.1.0, 5.0.0 to before 5.1.0, and 6.0.0 to before 6.4.0, a missing signature verification in User OIDC allowed a malicious ID4me authority to identify as any user. This issue has been patched in versions 3.1.0, 4.1.0, 5.1.0, 6.4.0 and 8.3.0.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Base score: 8.1

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.55%
Percentile among all scored CVEs: 44
Score date: 10/5/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1203 Exploitation for Client Executionexecution85 %
Primary impactT1078 Valid Accountsstealth · persistence · privilege escalation · initial access90 %
Secondary impactT1556 Modify Authentication Processdefense impairment · persistence · credential access75 %

Vector CVSS con UI:R (interacción del usuario) indica ejecución en el cliente (T1203). La falta de verificación de firma en OIDC permite suplantación de identidad (T1078) y manipulación de autenticación (T1556) desde una autoridad maliciosa.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

User Account Management Privileged Account Management Password Policies Multi-factor Authentication Application Developer Guidance Active Directory Configuration

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Nextcloud — User Oidc^AI

CWEs

CWE-287

References

Raw JSON (NVD)

Show

{
  "id": "CVE-2026-45156",
  "cveTags": [],
  "metrics": {
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          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
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            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
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          ],
          "version": "2.0.3",
          "timestamp": "2026-06-02T00:00:00+00:00"
        }
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          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N",
          "integrityImpact": "HIGH",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
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        "exploitabilityScore": 2.8
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  "affected": [
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  "published": "2026-06-01T17:17:09.283",
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      "url": "https://github.com/nextcloud/user_oidc/pull/1285",
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      "url": "https://hackerone.com/reports/3489490",
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      "value": "Nextcloud is an open source content collaboration platform. From versions 0.3.0 to before 3.1.0, 5.0.0 to before 5.1.0, and 6.0.0 to before 6.4.0, a missing signature verification in User OIDC allowed a malicious ID4me authority to identify as any user. This issue has been patched in versions 3.1.0, 4.1.0, 5.1.0, 6.4.0 and 8.3.0."
    },
    {
      "lang": "es",
      "value": "Nextcloud es una plataforma de colaboración de contenido de código abierto. Desde las versiones 0.3.0 hasta antes de la 3.1.0, 5.0.0 hasta antes de la 5.1.0, y 6.0.0 hasta antes de la 6.4.0, una verificación de firma faltante en User OIDC permitió a una autoridad ID4me maliciosa identificarse como cualquier usuario. Este problema ha sido parcheado en las versiones 3.1.0, 4.1.0, 5.1.0, 6.4.0 y 8.3.0."
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  "lastModified": "2026-07-22T07:10:00.107",
  "sourceIdentifier": "security-advisories@github.com"
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