Grav CMS EUVD-2026-62535

Exploitation requires an authenticated Grav user account with page-author permissions - a role that must be explicitly granted by an administrator and is not present by default on a fresh Grav installation with a single admin owner. The Twig sandbox must be active (it is the default sandboxing mode for page-author-level content in Grav). The vulnerability affects the default configuration of any Grav instance prior to 2.0.2 where at least one page-author account exists. Exploitation is strictly limited to confidentiality impact: no code execution, no file write, no availability impact. Attackers without an active page-author session cannot exploit this vulnerability remotely.

The CVSS 3.1 vector AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N scores 6.5, consistent with the description: the attack is network-reachable with no complexity barrier once an authenticated page-author account is held, with full confidentiality impact limited to data within the application. The PR:L prerequisite is the primary limiting factor - an attacker must already possess a page-author credential, which is a non-default, intentionally granted role. No EPSS score was included in the provided intelligence, so probabilistic exploitation likelihood cannot be quantified from this dataset; the absence should be noted rather than interpolated. The vulnerability is not listed in CISA KEV, and no standalone POC is confirmed beyond the public GitHub security advisory and commit diff, which together provide sufficient technical detail to reconstruct the attack. Real-world impact is significant for any multi-tenant or community-driven Grav deployment where untrusted contributors hold page-author permissions: credential exfiltration enables downstream account takeover against SMTP servers, external APIs, and databases referenced in plugin configuration - a meaningful blast radius despite the moderate CVSS score. Scope is unchanged (S:U), correctly reflecting that impact remains within the Grav application boundary even though harvested credentials may enable lateral movement outside it.

An attacker with a Grav page-author account edits or creates a page containing sandboxed Twig content such as {{ grav.offsetGet('config')|json_encode }} or {{ grav.offsetGet('config')|print_r }}, then previews or publishes the page to trigger sandbox rendering. The serialization filter bypasses GravSecurityPolicy and outputs the full plugins.* configuration tree - including SMTP credentials and API keys - in the rendered page response, which the attacker reads directly. No POC is publicly confirmed, but the public commit diff and advisory provide sufficient detail to reconstruct this technique without additional research.