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PatchSiren cyber security CVE debrief

CVE-2026-42562 alextselegidis CVE debrief

CVE-2026-42562 is a high-severity authorization flaw in Plainpad that lets a low-privilege authenticated user elevate themselves to administrator. The issue was publicly disclosed on 2026-05-09 and is fixed in Plainpad 1.1.1. Because the vulnerable behavior is reachable over the network by an authenticated account and can immediately unlock admin-only routes, organizations should treat this as a priority patching item.

Vendor
alextselegidis
Product
plainpad
CVSS
HIGH 8.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-09
Original CVE updated
2026-07-24
Advisory published
2026-05-09
Advisory updated
2026-07-24

Who should care

Administrators and operators of self-hosted Plainpad instances, especially environments that allow multiple authenticated users. Any deployment that trusts low-privilege accounts to update user records is exposed to privilege escalation until upgraded to 1.1.1.

Technical summary

According to the CVE description and GitHub advisory references, Plainpad accepted PUT /api.php/v1/users/{id} requests from authenticated users and persisted the admin attribute directly from user input. A low-privileged user could submit admin=true, have that value stored, and then immediately access routes intended only for administrators. The weakness is categorized as CWE-269 (Improper Privilege Management) and aligns with the supplied CVSS 3.1 vector AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L.

Defensive priority

High. This is an authenticated but straightforward privilege-escalation path that can turn a standard account into an administrator without user interaction. Patch quickly and verify no unauthorized admin accounts were created before remediation.

Recommended defensive actions

  • Upgrade Plainpad to version 1.1.1 or later as soon as possible.
  • Review any local changes or forks to confirm the admin field is no longer accepted from client-supplied input.
  • Audit user-management endpoints for mass-assignment or direct persistence of privilege fields such as admin.
  • Check logs for suspicious PUT /api.php/v1/users/{id} activity and investigate any changes that granted admin access.
  • Validate existing administrator accounts and revoke or reset any credentials, sessions, or tokens if unauthorized privilege escalation is suspected.

Evidence notes

The supplied source corpus ties this issue to the official NVD record, CVE record, GitHub issue 138, the 1.1.1 release, the security advisory GHSA-pvfv-wvpm-q6f6, and a fixing commit (9216a876d27b22c3d9259551636d803f7cb075fc). The NVD metadata lists CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L and CWE-269. No KEV entry was supplied.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-42562 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-42562

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

  • CVE-2026-42562 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-42562

    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.