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TI-2023-20846 Aliases CVE-2023-39953

Issuer not verified from obtained token in user_oidc

Priority LOW 23CWE-303Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
Low · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

user_oidc provides the OIDC connect user backend for Nextcloud, an open-source cloud platform. Starting in version 1.0.0 and prior to version 1.3.3, missing verification of the issuer would have allowed an attacker to perform a man-in-the-middle attack returning corrupted or known token they also have access to. user_oidc 1.3.3 contains a patch. No known workarounds are available.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00542 45th percentileScored 2026-11-07
Fix Fixed security-advisories (nextcloud): 1.3.3

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
nextcloudsecurity-advisories1.0.0 to before 1.3.31.3.3Patch availableCNA
  • security-advisories Vendornextcloud Affected 1.0.0 to before 1.3.3 Fixed in 1.3.3 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:nextcloud:user_oidc:*:*:*:*:*:*:*:*1.0.0 to before 1.3.3Vulnerablenextcloud
  • cpe:2.3:a:nextcloud:user_oidc:*:*:*:*:*:*:*:* Versions 1.0.0 to before 1.3.3 Vulnerable ·nextcloud

Remediation

  • Fix · CNA security-advisories (nextcloud) Fixed in 1.3.3

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2023-39953

References

Patch 2

Other 1

  • TI-2023-15378 Nextcloud user_oidc app is missing brute force protection CVSS 3.1CRITICAL 9.8
  • TI-2026-33084 Nextcloud: Wrong condition in the User OIDC app's LdapService allowed deleted LDAP users to authenticate CVSS 3.1HIGH 8.8
  • TI-2023-20847 user_oidc app stores client secret unencrypted in database CVSS 3.1HIGH 8.1
  • TI-2024-24824 Nextcloud user_oidc app's ID4me feature is available even when disabled CVSS 3.1MEDIUM 6.3
  • TI-2024-35183 Nextcloud User OIDC has an open redirection when logging in with User OIDC CVSS 3.1MEDIUM 6.1
  • TI-2026-33079 Nextcloud: Open Redirect in user_oidc login flow via protocol-relative URL bypass CVSS 3.1MEDIUM 6.1
See all 8 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences