CVE WatchAug 28, 2026

CVE-2023-49105

ownCloud Improper Authentication Vulnerability

CVSS

9.8

Critical

EPSS

43.2%

p99

KEV

YES

Aug 27, 2026

Exploit Today

0-100

Published: Nov 21, 2023 · Last modified: Aug 28, 2026 · CWE-287

EPSS · 30d

42.9%EPSS · 30 days43.2%

2026-09-292026-10-27

KEV catalog record

Product

ownCloud / ownCloud

Vulnerability

ownCloud Improper Authentication Vulnerability

Added to KEV

Aug 27, 2026

Remediate by

Aug 30, 2026

Known ransomware use

Summary description

ownCloud contains an improper authentication vulnerability that allows an attacker to access, modify, or delete any file without authentication if the username of a victim is known, and the victim has no signing-key configured.

Required action

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Notes

https://owncloud.org/security ; https://owncloud.com/security-advisories/webdav-api-authentication-bypass-using-pre-signed-urls/ ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2023-49105

Technical description

An issue was discovered in ownCloud owncloud/core before 10.13.1. An attacker can access, modify, or delete any file without authentication if the username of a victim is known, and the victim has no signing-key configured. This occurs because pre-signed URLs can be accepted even when no signing-key is configured for the owner of the files. The earliest affected version is 10.6.0.

Official references

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