CVE-2023-39953

Issuer not verified from obtained token in user_oidc

MEDIUM
4.8
CVSS Score
Published: August 10, 2023 at 01:55 PM UTC
Updated: June 17, 2026 at 06:13 AM UTC
1 product affected across 1 vendorUser Oidc

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Severity
MEDIUM4.8
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

95%
1.0.0 ≤ v < 1.3.3
Affected range stops below 1.3.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.8MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
HIGH
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-303

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