ownCloud ownCloud
CVE-2023-49105
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 this means for your business
- It affects ownCloud. It matters if your company, or a supplier that handles your data, runs it.
- Attackers are already using it. CISA added it to its list of flaws used in real attacks on 27 August 2026.
- An attacker can use it remotely, over a network, without a login, and without anyone at your company clicking anything.
- FIRST's prediction model gives it a 43% chance of attack attempts being seen in the next 30 days, ranking above 98% of all known flaws.
What to do
- 1Check whether your company or your suppliers run ownCloud, and which version. The affected versions are listed further down this page.
- 2If you do, apply the vendor's fix. A patch or vendor advisory has been published.
- 3Treat it as urgent. US federal agencies must fix it by 30 August 2026. That deadline does not apply to private companies, but it shows how seriously CISA takes it.
- 4Because attackers have used it, check the affected systems for signs of a break-in, not only for the update.
Not sure if your company is exposed?
Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.
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.
CISA’s wording, unedited. The notes it mentions are in CISA’s catalogue entry.
Scoring
- CVSS
- 9.8 (v3.1)
- Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H- Weakness
- CWE-287
- Assigned by
- cve@mitre.org
Dates
- Published
- 2026-08-27
- Last modified
- 2026-08-28
- Added to KEV
- 2026-08-27
- Remediation due
- 2026-08-30
- Sources
- CISA KEV, NVD
Affected products
- Owncloud Owncloud Server10.6.0 - 10.13.1
As listed in the NVD configuration data. Not a statement about your estate.