{"id":"GHSA-xhfv-7758-r9hx","summary":"Grav: Missing admin.super guard on core group blueprint access field allows admin.users operator to escalate to super-admin","details":"## Summary\nThe core Flex group blueprint `system/blueprints/user/group.yaml` (access field, lines 48-55) omits the `security@: admin.super` field guard that its sibling account blueprint carries (`account.yaml:131/138/150`, added by the CVE-2026-42613 fix). A delegated non-super operator holding `admin.users.update` can therefore save a group whose `access` map contains `admin.super: true`, which `UserGroupObject::authorize` then grants to every member of that group, a full privilege escalation to super-admin (scheduler/cron RCE, Twig eval). This is a distinct file, sink, and fix from all four related advisories.\n\n## Root Cause\nThe CVE-2026-42613 fix protected the account `access`/`groups` fields with a blueprint-level `security@: admin.super` gate, which `Blueprint::dynamicSecurity()` (`system/src/Grav/Common/Data/Blueprint.php:644-662`) uses to mark a field `validate.ignore=true` for non-super users so `BlueprintSchema::filterArray()` (`BlueprintSchema.php:263-311`) drops it. The functionally-identical group `access` field, a permission map granted to every member of the group, is declared in `system/blueprints/user/group.yaml:48-55` with `check_authorize: false` and NO `security@` guard. `check_authorize` has ZERO PHP enforcement (`grep -rn check_authorize` across the repo returns 0 PHP consumers; only two YAML blueprints reference it), so `security@` is the sole real control. Because the group access field lacks `security@`, `dynamicSecurity` never flags it, `filterArray` retains it, and `Validation::filterArray` (`type: array, value_type: bool`) passes the nested `admin.super:true` leaf through. The core save path (`FlexObject::update()` then `Framework/Flex/FlexObject.php:683` `$blueprint-\u003efilter($data,true,true)` then `save()`) persists it to `user://config/groups.yaml`.\n\n## Impact\nA delegated `admin.users` operator (strictly below `admin.super`) escalates to super-admin, gaining the admin panel, the scheduler (cron to RCE) and Twig evaluation. Full read/write/DoS (C:H/I:H/A:H). Even absent self-escalation, arbitrary rewrite of ANY group's ACL is itself a full escalation primitive.\n\n## Proof of Concept\nAs a non-super `admin.users` operator who is a member of group `ops`:\n```\nPOST /admin/accounts/groups/ops   (or groups.json task:save)\ndata[access][admin][super]=1\n```\n`user/config/groups.yaml` gains `ops: { access: { admin: { super: true } } }`, so the operator is super-admin on the next request.\n\n## Attack Chain\n1. Entry: authenticated delegated admin (`admin.users.update`, no `admin.super`) POSTs the group-edit form for a group they belong to (or a new group), body `access[admin][super]=true`. Guard: `FlexAuthorizeTrait::isAuthorizedAction` to `admin.users.update`. Bypass proof: `user-groups.yaml` exposes groups at `admin.users:crudl`; operator legitimately holds update.\n2. Check (field guard): `Blueprint::dynamicSecurity` marks `validate.ignore` only for `security@` fields. Guard: none on group access (no `security@`). Bypass proof: `group.yaml:48-55` has no `security@`; `git log -S 'security@' -- system/blueprints/user/group.yaml` is empty.\n3. Filter: `BlueprintSchema::filterArray` retains the non-ignored field; `Validation::filterArray` (`value_type: bool`) passes `admin.super:true` through. Bypass proof: field not flagged ignore/disabled; nested bool leaf preserved.\n4. Sink (persist): `FlexObject::update` then `filter` then `save` writes to `user://config/groups.yaml`. Guard: none. Bypass proof: value already survived steps 2/3; storage performs no ACL filtering.\n5. Impact: any member request triggers `UserGroupObject::authorize('admin.super')` (`.../UserGroups/UserGroupObject.php:75`) returning true, so the member is super-admin, enabling scheduler/Twig RCE.\n\n## Bypass Evidence\n- `system/blueprints/user/group.yaml:48-55`: access block with `check_authorize: false`, no `security@` (confirmed live on tag 2.0.12).\n- `git log -S 'security@' -- system/blueprints/user/group.yaml` is empty (guard never existed; a permanent gap, not a regression).\n- `git log 2.0.12..HEAD -- system/blueprints/user/group.yaml` is empty (no post-release fix).\n- `grep -rn check_authorize` (whole repo) returns 0 PHP hits (guard unenforced in PHP).\n- `grep -rn \"typePermissions|filterPermissions\" system/src/Grav/Common/Data` returns 0 (permissions map falls through to array-bool filtering that keeps nested keys).\n- Guard asymmetry: `account.yaml:131/138/150` carry `security@: admin.super`; `group.yaml` carries none. GHSA-h33v-82r9-v8pm's own text confirms the blueprint `security@` gate is the sole Flex-backend strip for these keys.\n\n## Affected Versions\n`\u003c= 2.0.12` (latest release; the guard never existed on `group.yaml`, so all 2.x are affected). The missing guard and the strip logic are both in core `getgrav/grav`; the group-edit UI is provided by the flex-objects/admin plugin, but the fix belongs in core.\n\n## Suggested Fix\nAdd `security@: admin.super` to the `access` field in `system/blueprints/user/group.yaml` (mirroring `account.yaml`), and/or enforce a super-only strip on group ACL saves in core so all callers are covered.\n\n---\nReported by **zx (Jace)** — GitHub: @manus-use","aliases":["CVE-2026-75837"],"modified":"2026-09-17T21:00:04.916301203Z","published":"2026-09-17T20:45:15Z","database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-09-17T20:45:15Z","nvd_published_at":null,"cwe_ids":["CWE-269","CWE-862"]},"references":[{"type":"WEB","url":"https://github.com/getgrav/grav/security/advisories/GHSA-xhfv-7758-r9hx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-75837"},{"type":"PACKAGE","url":"https://github.com/getgrav/grav"},{"type":"WEB","url":"https://www.vulncheck.com/advisories/grav-before-privilege-escalation-via-group-access-field"}],"affected":[{"package":{"name":"getgrav/grav","ecosystem":"Packagist","purl":"pkg:composer/getgrav/grav"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.0.14"}]}],"versions":["0.8.0","0.9.0","0.9.1","0.9.10","0.9.11","0.9.12","0.9.13","0.9.14","0.9.15","0.9.16","0.9.17","0.9.18","0.9.19","0.9.2","0.9.20","0.9.21","0.9.22","0.9.23","0.9.24","0.9.25","0.9.26","0.9.27","0.9.28","0.9.29","0.9.3","0.9.30","0.9.31","0.9.32","0.9.33","0.9.34","0.9.35","0.9.36","0.9.37","0.9.38","0.9.39","0.9.4","0.9.40","0.9.41","0.9.42","0.9.43","0.9.44","0.9.45","0.9.5","0.9.6","0.9.7","0.9.8","0.9.9","1.0.0","1.0.0-rc.1","1.0.0-rc.2","1.0.0-rc.3","1.0.0-rc.4","1.0.0-rc.5","1.0.0-rc.6","1.0.1","1.0.10","1.0.2","1.0.3","1.0.4","1.0.5","1.0.6","1.0.7","1.0.8","1.0.9","1.1.0","1.1.0-beta.1","1.1.0-beta.2","1.1.0-beta.3","1.1.0-beta.4","1.1.0-beta.5","1.1.0-rc.1","1.1.0-rc.2","1.1.0-rc.3","1.1.1","1.1.10","1.1.11","1.1.12","1.1.13","1.1.14","1.1.15","1.1.16","1.1.17","1.1.2","1.1.3","1.1.4","1.1.5","1.1.6","1.1.7","1.1.8","1.1.9","1.1.9-rc.1","1.1.9-rc.2","1.1.9-rc.3","1.2.0","1.2.0-rc.1","1.2.0-rc.2","1.2.0-rc.3","1.2.1","1.2.2","1.2.3","1.2.4","1.3.0","1.3.0-rc.1","1.3.0-rc.2","1.3.0-rc.3","1.3.0-rc.4","1.3.0-rc.5","1.3.1","1.3.10","1.3.2","1.3.3","1.3.4","1.3.5","1.3.6","1.3.7","1.3.8","1.3.9","1.4.0","1.4.0-beta.1","1.4.0-beta.2","1.4.0-beta.3","1.4.0-rc.1","1.4.0-rc.2","1.4.1","1.4.2","1.4.3","1.4.4","1.4.5","1.4.6","1.4.7","1.4.8","1.5.0","1.5.0-beta.1","1.5.0-beta.2","1.5.0-rc.1","1.5.1","1.5.10","1.5.2","1.5.3","1.5.4","1.5.5","1.5.6","1.5.7","1.5.8","1.5.9","1.6.0","1.6.0-beta.1","1.6.0-beta.2","1.6.0-beta.3","1.6.0-beta.4","1.6.0-beta.5","1.6.0-beta.6","1.6.0-beta.7","1.6.0-beta.8","1.6.0-rc.1","1.6.0-rc.2","1.6.0-rc.3","1.6.0-rc.4","1.6.1","1.6.10","1.6.11","1.6.12","1.6.13","1.6.14","1.6.15","1.6.16","1.6.17","1.6.18","1.6.19","1.6.2","1.6.20","1.6.21","1.6.22","1.6.23","1.6.24","1.6.25","1.6.26","1.6.27","1.6.28","1.6.29","1.6.3","1.6.30","1.6.31","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","1.7.0","1.7.0-beta.1","1.7.0-beta.10","1.7.0-beta.2","1.7.0-beta.3","1.7.0-beta.4","1.7.0-beta.5","1.7.0-beta.6","1.7.0-beta.7","1.7.0-beta.8","1.7.0-beta.9","1.7.0-rc.1","1.7.0-rc.10","1.7.0-rc.11","1.7.0-rc.12","1.7.0-rc.13","1.7.0-rc.14","1.7.0-rc.15","1.7.0-rc.16","1.7.0-rc.17","1.7.0-rc.18","1.7.0-rc.19","1.7.0-rc.2","1.7.0-rc.20","1.7.0-rc.3","1.7.0-rc.4","1.7.0-rc.5","1.7.0-rc.6","1.7.0-rc.7","1.7.0-rc.8","1.7.0-rc.9","1.7.1","1.7.10","1.7.12","1.7.13","1.7.14","1.7.15","1.7.16","1.7.17","1.7.18","1.7.19","1.7.20","1.7.21","1.7.22","1.7.23","1.7.24","1.7.25","1.7.26","1.7.26.1","1.7.27","1.7.27.1","1.7.28","1.7.29","1.7.29.1","1.7.3","1.7.30","1.7.31","1.7.32","1.7.33","1.7.34","1.7.35","1.7.36","1.7.37","1.7.37.1","1.7.38","1.7.39","1.7.39.1","1.7.39.2","1.7.39.3","1.7.39.4","1.7.4","1.7.40","1.7.41","1.7.41.1","1.7.41.2","1.7.42","1.7.42.1","1.7.42.2","1.7.42.3","1.7.43","1.7.44","1.7.45","1.7.46","1.7.47","1.7.48","1.7.49","1.7.49.1","1.7.49.2","1.7.49.3","1.7.49.4","1.7.49.5","1.7.5","1.7.51","1.7.52","1.7.53","1.7.53.1","1.7.53.2","1.7.53.3","1.7.6","1.7.7","1.7.8","1.7.9","1.8.0-beta.1","1.8.0-beta.10","1.8.0-beta.11","1.8.0-beta.12","1.8.0-beta.13","1.8.0-beta.14","1.8.0-beta.15","1.8.0-beta.16","1.8.0-beta.17","1.8.0-beta.18","1.8.0-beta.19","1.8.0-beta.2","1.8.0-beta.20","1.8.0-beta.21","1.8.0-beta.22","1.8.0-beta.23","1.8.0-beta.24","1.8.0-beta.25","1.8.0-beta.26","1.8.0-beta.27","1.8.0-beta.28","1.8.0-beta.29","1.8.0-beta.3","1.8.0-beta.4","1.8.0-beta.5","1.8.0-beta.6","1.8.0-beta.7","1.8.0-beta.8","1.8.0-beta.9","2.0.0","2.0.0-beta.1","2.0.0-beta.2","2.0.0-beta.3","2.0.0-beta.4","2.0.0-rc.1","2.0.0-rc.10","2.0.0-rc.2","2.0.0-rc.3","2.0.0-rc.4","2.0.0-rc.5","2.0.0-rc.6","2.0.0-rc.7","2.0.0-rc.8","2.0.0-rc.9","2.0.1","2.0.10","2.0.11","2.0.12","2.0.13","2.0.2","2.0.3","2.0.4","2.0.5","2.0.6","2.0.7","2.0.8","2.0.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-xhfv-7758-r9hx/GHSA-xhfv-7758-r9hx.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"}]}