CVE-2026-8135

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An rogue administrator with privileges to add blocks to an area can bypass the intended protection mechanism (_fromCIF === true), which normally restricts malicious inputs over form POST requests, by leveraging the REST API functionality. Because the REST API parses requests using json_decode(), the string \"true\" is evaluated as a strict PHP Boolean(true).\u00a0 This bypass allows the attacker to inject a malicious serialized payload \u00a0into the block's filterFields database column. The payload will subsequently be executed when the block's data is viewed or edited by an administrator leading to complete server takeover (RCE).The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 8.9 with a vector of\u00a0CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H.\u00a0 Thanks Nguy\u1ec5n V\u0103n Thi\u1ec7n https://github.com/Thien225409 \u00a0for reporting"}, {"lang": "es", "value": "Concrete CMS 9.5.0 y versiones anteriores es vulnerable a la ejecuci\u00f3n remota de c\u00f3digo debido a la deserializaci\u00f3n insegura que ocurre en el controlador de bloque ExpressEntryList. Un administrador malintencionado con privilegios para a\u00f1adir bloques a un \u00e1rea puede eludir el mecanismo de protecci\u00f3n previsto (_fromCIF === true), que normalmente restringe las entradas maliciosas a trav\u00e9s de solicitudes POST de formulario, aprovechando la funcionalidad de la API REST. Debido a que la API REST analiza las solicitudes usando json_decode(), la cadena 'true' se eval\u00faa como un booleano PHP estricto (true). Esta elusi\u00f3n permite al atacante inyectar una carga \u00fatil serializada maliciosa en la columna de la base de datos filterFields del bloque. La carga \u00fatil se ejecutar\u00e1 posteriormente cuando los datos del bloque sean vistos o editados por un administrador, lo que lleva a la toma de control completa del servidor (RCE). El equipo de seguridad de Concrete CMS otorg\u00f3 a esta vulnerabilidad una puntuaci\u00f3n CVSS v.4.0 de 8.9 con un vector de CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H. Gracias a Nguy?n V?n Thi?n https://github.com/Thien225409 por informar."}], "lastModified": "2026-07-23T16:10:00.137", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "435732F0-BA4B-4432-97EA-B730EBD44D4D", "versionEndIncluding": "9.5.0"}], "operator": "OR"}]}], "sourceIdentifier": "ff5b8ace-8b95-4078-9743-eac1ca5451de"}