CVE-2023-48239: nextcloud security-advisories · Improper Access Control
Affects nextcloud security-advisoriesSource CVE Database V5
Not known to be exploited · CVSS 8.5 High.
Data as of 25 Oct 2026, 19:02 UTC
- EPSS
- 0.9% chance of exploitation in 30 days – higher than 61% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:HExploitation evidence
Disclosed: evidence found.
CVE published 21 Nov 2023
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.
What to do
AI-suggested
1. Immediate upgrade to the patched Nextcloud Server or Enterprise Server versions as listed (e.g., 25.0.13, 26.0.8, 27.1.3, or corresponding Enterprise patches). 2. As a temporary workaround before patching, disable the 'files_external' app to prevent exploitation; note this disables external storage access but retains configurations. 3. Implement strict access controls and monitor user privileges to limit the number of users who can modify external storage configurations. 4. Audit external storage configurations regularly to detect unauthorized changes. 5. Employ network segmentation and firewall rules to restrict access to Nextcloud administrative interfaces. 6. Monitor logs for suspicious activities related to external storage updates. 7. Educate administrators about the vulnerability and ensure timely patch management processes are in place. 8. Consider deploying intrusion detection systems tailored to detect anomalous Nextcloud API calls or configuration changes.
Description
Nextcloud Server provides data storage for Nextcloud, an open source cloud platform. Starting in version 25.0.0 and prior to versions 25.0.13, 26.0.8, and 27.1.3 of Nextcloud Server and starting in version 20.0.0 and prior to versions 20.0.14.16, 21.0.9.13, 22.2.10.15, 23.0.12.12, 24.0.12.8, 25.0.13, 26.0.8, and 27.1.3 of Nextcloud Enterprise Server, a malicious user could update any personal or global external storage, making them inaccessible for everyone else as well. Nextcloud Server 25.0.13, 26.0.8, and 27.1.3 and Nextcloud Enterprise Server is upgraded to 20.0.14.16, 21.0.9.13, 22.2.10.15, 23.0.12.12, 24.0.12.8, 25.0.13, 26.0.8, and 27.1.3 contain a patch for this issue. As a workaround, disable app files_external. This workaround also makes the external storage inaccessible but retains the configurations until a patched version has been deployed.