CVE-2026-123792 Tiempos de análisis exponenciales y cuadráticos en el analizador YAML de Symfony

Afectados

• sensiolabs symfony

  hasta antes de 5.4.56desde 6.0.0 hasta antes de 6.4.50desde 7.0.0 hasta antes de 7.4.23desde 8.0.0 hasta antes de 8.1.11

Qué hacer

1. Verificá si usás symfony y en qué versión.
2. Actualizá a la versión corregida que indique el fabricante en su aviso o aplicá su mitigación.
3. Revisá registros y accesos de los sistemas expuestos para descartar un uso previo.

Calculadora CVSS

CVSS 4.0 · 8.7 ALTA

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

• Vector de ataqueRed
• Complejidad del ataqueBaja
• Requisitos del ataqueNinguno
• Privilegios requeridosNinguno
• Interacción del usuarioNinguna
• Confidencialidad (sistema vulnerable)Ninguna
• Integridad (sistema vulnerable)Ninguna
• Disponibilidad (sistema vulnerable)Alta
• Confidencialidad (sistemas posteriores)Ninguna
• Integridad (sistemas posteriores)Ninguna
• Disponibilidad (sistemas posteriores)Ninguna

Descripción original

The Symfony Yaml components Inline and Parser, parse some YAML documents inefficiently, so that a small crafted document can take disproportionately long to process, keeping a PHP process busy for seconds or minutes, potentially causing a denial of service in Symfony versions prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11. The parser repeats work it has already done in several places. An embedded mapping in a flow sequence is parsed again for every scalar appended to it, and so are the collections nested in it, so the parse time grows exponentially with the nesting depth. The patterns matching mapping keys and tags scan a run of spaces once per character of the run, and each scalar of a flow collection is matched against a copy of the rest of the collection, so the parse time grows quadratically with the size of the input. Nested blocks are also copied at each nesting level, which consumes memory as well as time. A few other constructs, such as an empty sequence item followed by a blank line or an anchor named 0, trigger similar repeated work. Any code parsing untrusted YAML is affected, with the default flags. In Symfony 7.4 and later, that includes #[MapRequestPayload] when the Yaml component is installed and the endpoint does not restrict acceptFormat. A single unauthenticated request with a YAML content type keeps a PHP worker busy until max_execution_time. JSON documents are valid YAML, so a JSON payload sent with a YAML content type is enough for the flow collection case. In Symfony 6.4, #[MapRequestPayload] accepts YAML only when the application registers a yaml request format.

Referencias (4)

• github.com/symfony/symfony/security/advisories/GHSA-hwfg-qwvh-2wfx
• github.com/symfony/symfony/commit/487f63bf2cacebc8ed8273c5c10d92955acd2402
• github.com/symfony/symfony/commit/08db22d52e5d3e6ec2f5c50db30a4d818100ffb9
• github.com/symfony/symfony/commit/49e03035eda3000e978a4612db74900013255ccd

Resumen traducido automáticamente de la descripción original. Fuente: Nureq Monitor. Cómo funciona.