GHSA-g7m4-839x-ch6v: spomky-labs/otphp Unbounded Digits Parameter Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-g7m4-839x-ch6v",
  "modified" : "2026-06-18T20:45:48Z",
  "published" : "2026-06-18T20:45:47Z",
  "aliases" : [ ],
  "summary" : "spomky-labs/otphp: Unbounded digits parameter in a provisioning URI triggers an uncaught DivisionByZeroError in OTP generation",
  "details" : "## Summary\n\nThe `digits` parameter parsed from a provisioning URI is validated only with a lower bound (`$value > 0`) and has no upper bound (`src/OTP.php:353-357`). OTP generation computes `$code % (10 ** $this->getDigits())` (`src/OTP.php:283`). When `digits` is large enough that `10 ** digits` overflows PHP's integer range and the `(int)` cast yields `0` (around `digits >= 40` on 64-bit PHP 8.x), the modulo operand becomes `0` and PHP raises a `DivisionByZeroError`.\n\n## Impact\n\n`OTPHP\\Factory::loadFromProvisioningUri()` forwards the attacker-controlled `digits` query value to `setParameter('digits', $value)`, so a hostile URI such as `otpauth://totp/Alice?secret=JBSWY3DPEHPK3PXP&digits=50` produces an OTP object whose `at()`, `now()`, and `verify()` all throw `DivisionByZeroError`. Because `DivisionByZeroError` extends `Error` (not `Exception`), callers that guard OTP generation with a `catch (\\Exception)` do not catch it, turning a malformed URI into an unhandled fatal error (denial of service of the verification path).\n\nMeasured threshold on PHP 8.3: `digits = 30` works, `digits >= 40` throws `DivisionByZeroError: Modulo by zero`.\n\n## Affected component\n\n- `src/OTP.php:353-357` — `digits` parameter callback (no upper bound)\n- `src/OTP.php:283` — `$code % (10 ** $this->getDigits())`\n\n## Proof of concept\n\n```php\nuse OTPHP\\Factory;\nuse OTPHP\\InternalClock;\n\n$otp = Factory::loadFromProvisioningUri(\n    'otpauth://totp/Alice?secret=JBSWY3DPEHPK3PXP&digits=50',\n    new InternalClock()\n);\n$otp->at(0); // DivisionByZeroError: Modulo by zero (escapes catch (\\Exception))\n```\n\n## Remediation\n\nEnforce a sane upper bound on `digits` in the parameter validation callback (e.g. reject values above 8–10, the practical range for OTPs) so that an out-of-range value is rejected with a documented exception instead of producing an object that fails later with an uncatchable `Error`.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "spomky-labs/otphp"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "11.4.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/Spomky-Labs/otphp/security/advisories/GHSA-g7m4-839x-ch6v"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/spomky-labs/otphp/GHSA-g7m4-839x-ch6v.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/Spomky-Labs/otphp"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1284", "CWE-369" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-18T20:45:47Z",
    "nvd_published_at" : null
  }
}