CVE-2026-45077: Symfony/monolog bridge Log Listener Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-m7v2-7gxm-vc2v",
  "modified" : "2026-05-27T21:13:29Z",
  "published" : "2026-05-27T21:13:29Z",
  "aliases" : [ "CVE-2026-45077" ],
  "summary" : "Symfony has Unauthenticated PHP Object Deserialization in MonologBridge server:log Listener",
  "details" : "### Description\n\n`Symfony\\Bridge\\Monolog\\Command\\ServerLogCommand` (the `server:log` console command) is a development-time helper that opens a TCP listener and displays log records pushed to it by the application's logging pipeline. Two unsafe defaults combine into a remotely reachable PHP object-deserialization sink:\n\n1. The listener binds to `0.0.0.0:9911` by default; it accepts connections on every interface, not only loopback.\n2. Each received frame is processed as `unserialize(base64_decode($message))` without an `allowed_classes` allowlist, without authentication, and without any integrity check. The decoded value is then passed to `displayLog(..., array $record)` which assumes (without validating) that the result is an array.\n\nAny host that can reach TCP port 9911 on a machine running `server:log` can therefore submit attacker-chosen serialized PHP payloads. The minimum impact is an unauthenticated denial of service (sending a non-array, e.g. `serialize(new stdClass())`, crashes the listener with a type error). Object injection with magic-method side effects (`__wakeup()` / `__destruct()` / etc.) is reachable before the array type-check fires; full remote code execution is environment-dependent and contingent on usable gadget chains in the autoload set of the target process.\n\n### Resolution\n\nThe `server:log` command no longer binds to all interfaces by default: the default `--host` is now `127.0.0.1:9911`, requiring explicit opt-in to accept off-host traffic. Message decoding is gated by an `unserialize()` allowlist restricted to the `Symfony\\Component\\VarDumper\\Caster\\*` and `Symfony\\Component\\VarDumper\\Cloner\\*` classes that legitimately appear inside dumped log records; any other class is rejected and the record discarded.\n\nThe patch for this issue is available [here](https://github.com/symfony/symfony/commit/0891b2f293896c488e26943dc034334364b77fc4) for branch 5.4.\n\n### Credits\n\nSymfony would like to thank Toàn Thắng and Sam Sanoop for reporting the issue and Nicolas Grekas for fixing it.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "symfony/monolog-bridge"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.4.52"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "symfony/symfony"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.4.52"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "symfony/monolog-bridge"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "6.0.0"
      }, {
        "fixed" : "6.4.40"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "symfony/monolog-bridge"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.0.0"
      }, {
        "fixed" : "7.4.12"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "symfony/monolog-bridge"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "8.0.0"
      }, {
        "fixed" : "8.0.12"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "symfony/symfony"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "6.0.0"
      }, {
        "fixed" : "6.4.40"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "symfony/symfony"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.0.0"
      }, {
        "fixed" : "7.4.12"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "symfony/symfony"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "8.0.0"
      }, {
        "fixed" : "8.0.12"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/symfony/symfony/security/advisories/GHSA-m7v2-7gxm-vc2v"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/symfony/symfony/commit/0891b2f293896c488e26943dc034334364b77fc4"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/monolog-bridge/CVE-2026-45077.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-45077.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/symfony/symfony"
  }, {
    "type" : "WEB",
    "url" : "https://symfony.com/cve-2026-45077"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-502", "CWE-668" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-27T21:13:29Z",
    "nvd_published_at" : null
  }
}