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VulnerabilityPublished Updated

CVE-2026-45156: nextcloud security-advisories · Improper Authentication

Affects nextcloud security-advisoriesSource CVE Database V5

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Not known to be exploited · CVSS 8.1 High · fixed in 6.4.0 : patch nextcloud security-advisories soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
8.1High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 35% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 6.4.0, 5.1.0, 3.1.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 1 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    Public exploit code: GitHub proofs of concept

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), GitHub proofs of concept, the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade security-advisories and nextcloud/user_oidc to 6.4.0, 5.1.0 or 3.1.0.

Affected software

ProductAffectedFixed in
nextcloudsecurity-advisoriesAffected
  • >=6.0.0 <6.4.0
Fixed in
  • 6.4.0
nextcloudsecurity-advisoriesAffected
  • >=5.0.0 <5.1.0
Fixed in
  • 5.1.0
nextcloudsecurity-advisoriesAffected
  • >=0.3.0 <3.1.0
Fixed in
  • 3.1.0
GitHubnextcloud/user_oidcpkg:github/nextcloud/user_oidcOther threatsAffected
  • 0.3.0 <3.1.0
  • 5.0.0 <5.1.0
  • 6.0.0 <6.4.0
Fixed in
  • 3.1.0
  • 5.1.0
  • 6.4.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in Nextcloud versions 3.1.0, 4.1.0, 5.1.0, 6.4.0, and 8.3.0. Users running affected versions should upgrade to one of these patched versions to remediate the vulnerability. Since this is not a cloud service, remediation depends on user action to update their installations. Patch status is confirmed by the vendor advisory information embedded in the description.

Description

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.

References

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