Security readout for executives and security teams
Plain-English summary
Some supported Nextcloud Server versions did not rate-limit a public share-link mount endpoint. An unauthenticated internet user may have been able to probe for potentially valid public share tokens. The vendor fixed this in 19.0.13, 20.0.11, and 21.0.3, with no known workaround stated.
Executive priority
Treat as a moderate-priority patch for any exposed Nextcloud deployment. It can support discovery of valid public share tokens, which may increase data-sharing risk, but supplied evidence does not show active exploitation or a broader compromise primitive.
Technical view
CVE-2021-32741 is a CWE-799 rate-limiting flaw in Nextcloud Server public share link mounting. The supplied CVSS v3.1 vector is AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N, score 5.3. Affected ranges are below 19.0.13, 20.0.0 through below 20.0.11, and 21.0.0 through below 21.0.3.
Likely exposure
Exposure is most likely for internet-reachable Nextcloud Server instances with public sharing enabled and versions in the affected ranges. Internal-only instances still have risk from any user or network path that can reach the public share mount endpoint.
Exploitation context
The source bundle does not show CISA KEV listing or confirmed active exploitation. The risk is unauthenticated token enumeration against public share links due to missing rate limiting, not a full server takeover based on supplied evidence.
Researcher notes
Evidence is limited to the advisory, CVE record, pull request, and HackerOne reference. The supplied data identifies the weakness and fixed versions, but does not provide a named workaround or confirmed exploitation in the wild.
Mitigation direction
- Upgrade Nextcloud Server to 19.0.13, 20.0.11, 21.0.3, or later supported versions.
- Do not rely on a workaround; the advisory states none are known.
- Review vendor security advisory and release guidance for environment-specific upgrade sequencing.
- Assess public share exposure and reduce unnecessary public links where operationally feasible.
Validation and detection
- Inventory Nextcloud Server versions and compare them to the affected ranges.
- Confirm public share link functionality is running on a fixed version after upgrade.
- Review access logs for unusual repeated activity against public share link mount paths.
- Verify security monitoring flags high-rate unauthenticated requests to sharing endpoints.
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-799: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-32741 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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:N/I:L/A:N3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-crvj-vmf7-xrvrCVE reference · x_refsource_CONFIRM
- https://github.com/nextcloud/server/pull/26958CVE reference · x_refsource_MISC
- https://hackerone.com/reports/1192144CVE 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.
Improper Control of Interaction Frequency
Improper Control of Interaction Frequency represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.