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Grav: Missing admin.super guard on core group blueprint access field allows admin.users operator to escalate to super-admin

High severity GitHub Reviewed Published Aug 3, 2026 in getgrav/grav • Updated Sep 17, 2026

Package

composer getgrav/grav (Composer)

Affected versions

< 2.0.14

Patched versions

2.0.14

Description

Summary

The 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.

Root Cause

The 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 $blueprint->filter($data,true,true) then save()) persists it to user://config/groups.yaml.

Impact

A 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.

Proof of Concept

As a non-super admin.users operator who is a member of group ops:

POST /admin/accounts/groups/ops   (or groups.json task:save)
data[access][admin][super]=1

user/config/groups.yaml gains ops: { access: { admin: { super: true } } }, so the operator is super-admin on the next request.

Attack Chain

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.

Bypass Evidence

  • system/blueprints/user/group.yaml:48-55: access block with check_authorize: false, no security@ (confirmed live on tag 2.0.12).
  • git log -S 'security@' -- system/blueprints/user/group.yaml is empty (guard never existed; a permanent gap, not a regression).
  • git log 2.0.12..HEAD -- system/blueprints/user/group.yaml is empty (no post-release fix).
  • grep -rn check_authorize (whole repo) returns 0 PHP hits (guard unenforced in PHP).
  • grep -rn "typePermissions|filterPermissions" system/src/Grav/Common/Data returns 0 (permissions map falls through to array-bool filtering that keeps nested keys).
  • 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.

Affected Versions

<= 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.

Suggested Fix

Add 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.

Reported by zx (Jace) — GitHub: @manus-use

References

@rhukster rhukster published to getgrav/grav Aug 3, 2026
Published to the GitHub Advisory Database Sep 17, 2026
Reviewed Sep 17, 2026
Last updated Sep 17, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity High
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
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

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(41st percentile)

Weaknesses

Improper Privilege Management

The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. Learn more on MITRE.

Missing Authorization

The product does not perform an authorization check when an actor attempts to access a resource or perform an action. Learn more on MITRE.

CVE ID

CVE-2026-75837

GHSA ID

GHSA-xhfv-7758-r9hx

Source code

Credits

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