      return function verify(data, signature, algo) {
        const pem = this[SYM_PUB_PEM];
        if (pem === null)
          return new Error('No public key available');
        if (!algo || typeof algo !== 'string')
          algo = this[SYM_HASH_ALGO];
        try {
          return verify_(algo, data, pem, signature);
        } catch (ex) {
          return ex;
        }
      };
The software constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.