CVE-2023-49105: ownCloud Improper Authentication Vulnerability
What it is
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.
What to do
Treat this as urgent. Identify every affected system, starting with anything internet-facing, and apply the vendor fix or mitigation within days. If you cannot patch quickly, isolate or disable the affected service and watch for signs of compromise.
- Priority
- Act now: Patch or mitigate internet-facing systems within days.
- Severity (CVSS)
- 9.8 critical
- CISA assessment (SSVC)
- actively exploited; attackers can automate it at scale; total control of the affected system
- Exploit probability (EPSS, 30 days)
- 43%, higher than 98% of all CVEs
- Added to CISA KEV
- 27 August 2026
- CISA fix-by date
- 30 August 2026 (US federal agencies; a sensible deadline for everyone)
- Ransomware use
- Not known
- Weakness
- CWE-287
References
- NIST NVD entry
- CISA KEV entry
- owncloud.com/security-advisories/webdav-api-authentication-bypass-using-pre-sign
- owncloud.org/security
- owncloud.com/security-advisories/webdav-api-authentication-bypass-using-pre-sign
- owncloud.org/security
- hunt.io/blog/chinese-speaking-operator-philippine-nuclear-naval-contractor
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-49105
Sources: CISA Known Exploited Vulnerabilities · FIRST Exploit Prediction Scoring System (EPSS) · NIST National Vulnerability Database · CISA Vulnrichment (SSVC), via the CVE Program. This product uses data from the NVD API but is not endorsed or certified by the NVD. Summaries are machine-written from CISA’s description; treat the vendor’s advisory as the authority for fixes.