Security readout for executives and security teams
Plain-English summary
CVE-2021-43863 affects the Nextcloud Android app before 3.18.1. A malicious app already installed on the same Android device could bypass normal permission controls and read Nextcloud data. This is primarily a mobile endpoint data-confidentiality risk, not evidence of remote compromise of the Nextcloud server.
Executive priority
Treat this as a high-priority mobile data exposure issue. Prioritize updating managed Android clients and assessing BYOD exposure. Server-side patching alone is not enough because the vulnerable component is the Android client.
Technical view
The issue involves Nextcloud Android content providers. FileContentProvider is affected by SQL injection, and DiskLruImageCacheFileProvider has insufficient permission control. Before 3.18.1, these provider flaws could let a same-device malicious app access Nextcloud app data outside the intended Android permission boundary.
Likely exposure
Organizations are exposed where users run the Nextcloud Android client below 3.18.1, especially on unmanaged or BYOD Android devices where malicious or sideloaded apps may coexist with business file-sync data.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation evidence. The described attacker is a malicious Android app on the same device, so practical risk depends on endpoint app hygiene and affected client deployment.
Researcher notes
Evidence supports a client-side confidentiality issue in Nextcloud Android before 3.18.1. The bundle names SQL injection in FileContentProvider and permission-control weakness in DiskLruImageCacheFileProvider. No workaround is identified besides upgrade. Avoid assuming server compromise or active exploitation without additional sources.
Mitigation direction
- Upgrade the Nextcloud Android app to version 3.18.1 or later.
- Use MDM or app-store controls to force the updated client version.
- For devices that cannot update, check current Nextcloud vendor guidance.
- Reduce risk from untrusted Android apps on devices using Nextcloud.
Validation and detection
- Inventory Android devices running the Nextcloud app and record installed versions.
- Confirm all managed installations are version 3.18.1 or later.
- Identify unmanaged or BYOD usage where app version visibility is limited.
- Review whether affected devices store sensitive Nextcloud-synced business data.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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CWE-89: Database access and collection lookup
Injection into data stores can inform collection, data access, and exfiltration detection reviews. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupDatabase behavior lookup
The CVE wording references database injection or access, so collection and exfiltration review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-43863 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/nextcloud/android/security/advisories/GHSA-vjp2-f63v-w479CVE reference · x_refsource_CONFIRM
- https://github.com/nextcloud/android/commit/627caba60e69e223b0fc89c4cb18eaa76a95db95CVE reference · x_refsource_MISC
- https://hackerone.com/reports/1358597CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.