Default settings leak federated cloud ID to lookup server of all users
Nextcloud Server is a Nextcloud package that handles data storage. Nextcloud Server versions prior to 19.0.11, 20.0.10, or 21.0.2 send user IDs to the lookup server even if the user has no fields set to published. The vulnerability is patched in versions 19.0.11, 20.0.10, and 21.0.2; no workarounds outside the updates are known to exist.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for help- Published
- Jun 1, 2021
- Updated
- Jun 16, 2026
- EPSS
- 1.2% · 67th percentile
- CWE
- CWE-201
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Report tools
Action score
10
Monitor
Low priority for now.
- CVSS
- 10 / 40 · 2.7 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 1.2%
CNA vs NVD score
- NVD
- 2.7
- CNA · GitHub_M
- 2.7
- agree
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| nextcloud | nextcloud server | cpe:2.3:a:nextcloud:nextcloud_server |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- nextcloud nextcloud serverbefore 19.0.11
- nextcloud nextcloud server20.0.0 and later · before 20.0.10
- nextcloud nextcloud server21.0.0 and later · before 21.0.2
Versions reported by the vendor
Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.
nextcloud security-advisories
- < 19.0.11, >= 20.0.0, < 20.0.10, >= 21.0.0, < 21.0.2affected
Same product
nextcloud: all recordsOther highest-scoring records for the same primary product.
- CVE-2021-32802Preview generation used third-party library not suited for user-generated content in Nextcloud server40Plan
- CVE-2021-32726Webauthn tokens not removed after user has been deleted40Plan
- CVE-2021-22915Nextcloud server before 19.0.11, 20.0.10, 21.0.2 is vulnerable to brute force attacks due to lack of inclusion of IPv6 subnets in rate-limit40Plan
- CVE-2023-49792Bruteforce protection can be bypassed with misconfigured proxy39Monitor
- CVE-2023-48306Nextcloud Server DNS pin middleware can be tricked into DNS rebinding allowing SSRF39Monitor
- CVE-2021-32654Attacker can obtain write access to any federated share/public link37Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
No fix version is recorded for this entry. Check the references for vendor advisories.
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- Administrator privileges are required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- low · data can be read
- Integrity
- none
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- Low
- Integrity impact
- None
- Availability impact
- None
Weakness class (CWE)
CWE-201 · Insertion of Sensitive Information Into Sent DataCVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Choosing Message IdentifierCAPEC-12likelihood: High · High
- Exploiting Incorrectly Configured SSL/TLSCAPEC-217likelihood: Low
- WiFi MAC Address TrackingCAPEC-612Low
- WiFi SSID TrackingCAPEC-613Low
- Cellular Broadcast Message RequestCAPEC-618Low
- Signal Strength TrackingCAPEC-619Low
- Analysis of Packet Timing and SizesCAPEC-621Low
- Electromagnetic Side-Channel AttackCAPEC-622Low
ATT&CK techniques
—
Change log
No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.
References
- github.com/nextcloud/security-advisories/security/advisories/GHSA-396j-vqpr-qg45
- hackerone.com/reports/1173436
- security.gentoo.org/glsa/202208-17
Vendor advisories and official records. Exploit/PoC links are deliberately left out.