CVE-2023-48304Network attack vector

Calendar disruption via missing CalDAV owner check

Published Nov 21, 2023 · Updated Aug 2, 2024

Authorization bypass in Nextcloud Server and Enterprise Server allows remote authenticated users to toggle another user's birthday calendar. The CalDAV birthday-calendar handler accepted POST requests for a target calendar home without verifying that its owner matched the authenticated user. Any account on the same server can reach this path, and the effect is limited to enabling or disabling the target user's generated birthday calendar.

CVSS severity4.3
Medium
EPSS probability0.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization bypass in Nextcloud Server and Enterprise Server allows remote authenticated users to toggle another user's birthday calendar. The CalDAV birthday-calendar handler accepted POST requests for a target calendar home without verifying that its owner matched the authenticated user. Any account on the same server can reach this path, and the effect is limited to enabling or disabling the target user's generated birthday calendar.

The record

CVE
CVE-2023-48304
Published
Nov 21, 2023
Updated
Aug 2, 2024
Vendor
Nextcloud GmbH
Product
Security Advisories
Classifications
CWE-639, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 21, 2023CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 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=>= 22.0.0, < 22.2.10.16
  2. Affected versionversion=>= 23.0.0, < 23.0.12.11
  3. Affected versionversion=>= 24.0.0, < 24.0.12.7
  4. Affected versionversion=>= 25.0.0, < 25.0.11
  5. Affected versionversion=>= 26.0.0, < 26.0.6
  6. Affected versionversion=>= 27.0.0, < 27.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Security Advisoriesversion=>= 22.0.0, < 22.2.10.16; version=>= 23.0.0, < 23.0.12.11; version=>= 24.0.0, < 24.0.12.7; version=>= 25.0.0, < 25.0.11; version=>= 26.0.0, < 26.0.6; version=>= 27.0.0, < 27.1.0

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
4.3GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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-639Authorization Bypass Through User-Controlled Key
T1499Endpoint Denial of Service

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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