CVE-2023-39963

Account takeover via unconfirmed app-password creation

Published Aug 10, 2023 · Updated Oct 10, 2024

Improper access control in affected Nextcloud Server releases allows attackers with a stolen user session to create app passwords. The getapppassword endpoint generated a new application credential without enforcing the password confirmation required for sensitive actions. A valid hijacked session is required, after which the resulting app password authenticates to the victim's account.

CVSS severity8.1
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in affected Nextcloud Server releases allows attackers with a stolen user session to create app passwords. The getapppassword endpoint generated a new application credential without enforcing the password confirmation required for sensitive actions. A valid hijacked session is required, after which the resulting app password authenticates to the victim's account.

The record

CVE
CVE-2023-39963
Published
Aug 10, 2023
Updated
Oct 10, 2024
Vendor
Nextcloud GmbH
Product
Security Advisories
Classifications
CWE-284, T1098
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 10, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 10, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=>= 20.0.0, < 20.0.14.15
  2. Affected versionversion=>= 21.0.0, < 21.0.9.13
  3. Affected versionversion=>= 22.0.0, < 22.2.10.14
  4. Affected versionversion=>= 23.0.0, < 23.0.12.9
  5. Affected versionversion=>= 24.0.0, < 24.0.12.5
  6. Affected versionversion=>= 25.0.0, < 25.0.9
  7. Affected versionversion=>= 26.0.0, < 26.0.4
  8. Affected versionversion=>= 27.0.0, < 27.0.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Security Advisoriesversion=>= 20.0.0, < 20.0.14.15; version=>= 21.0.0, < 21.0.9.13; version=>= 22.0.0, < 22.2.10.14; version=>= 23.0.0, < 23.0.12.9; version=>= 24.0.0, < 24.0.12.5; version=>= 25.0.0, < 25.0.9; version=>= 26.0.0, < 26.0.4; version=>= 27.0.0, < 27.0.1

Published CVSS scores

8.1GitHub Security AdvisoryCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L

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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control
T1098Account Manipulation

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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