PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-45267 nextcloud CVE debrief

A missing authorization check in Nextcloud Forms allowed authenticated users to read form submissions belonging to other users. The vulnerability was disclosed via GitHub Security Advisories and HackerOne, with a fix released in version 5.2.6. No known exploitation in ransomware campaigns has been reported.

Vendor
nextcloud
Product
security-advisories
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-01
Original CVE updated
2026-07-22
Advisory published
2026-06-01
Advisory updated
2026-07-22

Who should care

Organizations running Nextcloud Forms versions prior to 5.2.6, particularly those hosting multi-user instances where form data confidentiality is required. Security teams responsible for access control validation in content collaboration platforms should prioritize patching.

Technical summary

Nextcloud Forms, prior to version 5.2.6, failed to enforce proper authorization checks when handling requests to read form submissions. An authenticated attacker could exploit this flaw to access form submission data belonging to other users. The vulnerability is classified under CWE-862 (Missing Authorization) and CWE-200 (Information Exposure), with a CVSS 3.1 base score of 6.5 (Medium severity). The issue has been resolved in version 5.2.6 via a patch referenced in GitHub pull request #3269.

Defensive priority

medium

Recommended defensive actions

  • Upgrade Nextcloud Forms to version 5.2.6 or later to remediate the missing authorization check.
  • Review form submission access logs for unauthorized read activity by non-owning users prior to patching.
  • Validate that role-based access controls for form submissions enforce ownership or explicit sharing permissions after upgrade.

Evidence notes

The CVE description states that prior to version 5.2.6, a missing permissions check allowed users to request reading form submissions of other users. The NVD record lists the vulnerability status as Deferred. CVSS 3.1 vector AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N yields a base score of 6.5 (Medium). Weaknesses identified as CWE-200 (Information Exposure) and CWE-862 (Missing Authorization). The fix is referenced in GitHub pull request #3269 and security advisory GHSA-r4gh-f8x6-m55f. A HackerOne report (#3628817) is also associated with this disclosure.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-45267 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-45267

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-45267 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-45267

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.