CVE-2023-35927Network attack vector

System-addressbook tampering via writable CardDAV ACLs

Published Jun 23, 2023 · Updated Nov 7, 2024

Improper access control in Nextcloud Server and Enterprise Server allows remote authenticated users to alter system-addressbook VCards. CardDAV system-addressbook ACLs fail to mark the collection read-only, allowing a federated peer to submit writes and deletions instead of limiting updates to the DAV backend. Exploitation requires mutually trusted servers with exchanged share secrets; altered contacts affect user search and avatar displays until affected users update their profile data.

CVSS severity7.6
High
EPSS probability0.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper access control in Nextcloud Server and Enterprise Server allows remote authenticated users to alter system-addressbook VCards. CardDAV system-addressbook ACLs fail to mark the collection read-only, allowing a federated peer to submit writes and deletions instead of limiting updates to the DAV backend. Exploitation requires mutually trusted servers with exchanged share secrets; altered contacts affect user search and avatar displays until affected users update their profile data.

The record

CVE
CVE-2023-35927
Published
Jun 23, 2023
Updated
Nov 7, 2024
Vendor
Nextcloud GmbH
Product
Security Advisories
Classifications
CWE-284, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 23, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 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=Nextcloud Enterprise Server >= 21.0.0, < 21.0.9.12
  2. Affected versionversion=Nextcloud Enterprise Server >= 22.0.0, < 22.2.10.12
  3. Affected versionversion=Nextcloud Enterprise Server >= 23.0.0, < 23.0.12.7
  4. Affected versionversion=Nextcloud Enterprise Server >= 24.0.0, < 24.0.12.2
  5. Affected versionversion=Nextcloud Enterprise Server >= 25.0.0, < 25.0.7
  6. Affected versionversion=Nextcloud Enterprise Server >= 26.0.0, < 26.0.2
  7. Affected versionversion=Nextcloud Server >= 25.0.0, < 25.0.7
  8. Affected versionversion=Nextcloud Server >= 26.0.0, < 26.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Security Advisoriesversion=Nextcloud Enterprise Server >= 21.0.0, < 21.0.9.12; version=Nextcloud Enterprise Server >= 22.0.0, < 22.2.10.12; version=Nextcloud Enterprise Server >= 23.0.0, < 23.0.12.7; version=Nextcloud Enterprise Server >= 24.0.0, < 24.0.12.2; version=Nextcloud Enterprise Server >= 25.0.0, < 25.0.7; version=Nextcloud Enterprise Server >= 26.0.0, < 26.0.2; version=Nextcloud Server >= 25.0.0, < 25.0.7; version=Nextcloud Server >= 26.0.0, < 26.0.2

Published CVSS scores

8.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
7.6GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control
T1565.001Stored Data 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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo