CVE-2026-45691Network attack vector

Two-factor authentication bypass via session-token replay

Published Jun 1, 2026 · Updated Jun 1, 2026

Improper authentication in Nextcloud Server 32.0.0 through 32.0.8 and 33.0.0 through 33.0.2 allows remote authenticated users to bypass 2FA. User\Session::tryTokenLogin accepts a temporary pre-2FA session token from an Authorization Bearer header, although that token should remain cookie-bound. Possession of a password-authenticated session cookie before TOTP completion is required, after which DAV resources can be read or written without the second factor.

CVSS severity5.9
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authentication in Nextcloud Server 32.0.0 through 32.0.8 and 33.0.0 through 33.0.2 allows remote authenticated users to bypass 2FA. User\Session::tryTokenLogin accepts a temporary pre-2FA session token from an Authorization Bearer header, although that token should remain cookie-bound. Possession of a password-authenticated session cookie before TOTP completion is required, after which DAV resources can be read or written without the second factor.

The record

CVE
CVE-2026-45691
Published
Jun 1, 2026
Updated
Jun 1, 2026
Vendor
Nextcloud GmbH
Product
Security Advisories
Classifications
CWE-287, T1550.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 32.0.0, < 32.0.9
  2. Affected versionversion=>= 33.0.0, < 33.0.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Security Advisoriesversion=>= 32.0.0, < 32.0.9; version=>= 33.0.0, < 33.0.3

Published CVSS scores

5.9GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1550.004Web Session Cookie

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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