CVE-2023-39953 Issuer not verified from obtained token in user_oidc

What is CVE-2023-39953?

CVE-2023-39953 is a medium-severity authentication bypass vulnerability in nextcloud security-advisories, published on 10 Aug 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-303

Which versions are affected by CVE-2023-39953?

It affects 1 product.

Products include Nextcloud User Oidc.

How do I fix CVE-2023-39953?

No fix has been published for CVE-2023-39953 yet. Limit exposure of the affected software until one is available.

Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.

Is CVE-2023-39953 being exploited?

There is no known exploitation of CVE-2023-39953 in the wild and no public exploit code.

Other vulnerabilities in nextcloud security-advisories

• CVE-2023-32074 Nextcloud user_oidc app is missing brute force protection High 8.0
• CVE-2024-37312 Nextcloud user_oidc app's ID4me feature is available even when disabled Medium 6.3
• CVE-2024-37886 Nextcloud user_oidc's ID4me does not validate signature or expiration Medium 5.4
• CVE-2023-28848 CSRF protection on user_oidc login returned the expected token in case of an error Medium 4.8
• CVE-2026-45284 Nextcloud: Wrong condition in the User OIDC app's LdapService allowed deleted LDAP users to authenticate Medium 4.6

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-xx3h-v363-q36j.