Browser-trusted certificate authority (CA) Comodo said it mistakenly issued transport layer security credentials for "mailarchive," "help," and at least five other forbidden names and warned that "quite a number" of unnamed competitors have committed similar violations.

The non-compliant certificates are forbidden under the baseline requirements enforced by the CA Browser Forum, an industry group of CAs and browser makers that establish rules CAs must follow for their digital certificates to be trusted in Chrome, Internet Explorer, and other major browsers. The rules forbid the issuance of certificates for internal names that aren't part of a valid Internet domain name or for a reserved IP address such as 192.168.1.1.

The rules are designed to prevent the issuance of certificates for names such as “exchange,” “mailserver,” “domain," or "localhost," which many operating systems and organizations use to designate internal servers or other resources. The regulations similarly bar certificates for public IP addresses reserved for routers or other internal resources inside a home or organization network. A CA-issued certificate for something as generic as "mailserver" or "192.168.1.1," for instance, could be used to spy on or impersonate any resource that used that name or IP address. The baseline requirements bar all CAs from issuing certificates with such internal names or IP addresses and expire after November 1, 2015.

In an incident report published Monday, Rob Stradling, a senior research and development scientist at Comodo, said his team conducted a search on November 5 and found the company had issued eight credentials that didn't comply with those rules. The most potentially dangerous violations included a common name or subject alternative name of help and mailarchive. The violations came four years after Comodo defenses were breached by hackers who used their access to the company's computers to counterfeit browser-trusted certificates for highly sensitive Gmail, Skype, Mozilla, and Microsoft domains.

"If someone steals the certificate and puts it inside some other corporate network, this gives whoever owns the certificate the ability to spoof 'help,' whatever that means," Nick Sullivan, head of security engineering at CloudFlare, told Ars.

Stradling said the misissued credentials were the result of a subtle bug that allowed certificates to be issued even when they contained the restricted internal names. The bug has been fixed and Comodo engineers are now updating quality control measures to make sure non-compliant certificates are detected earlier in the issuance process. Stradling went on to warn that the practice isn't limited to Comodo.

"We widened our investigation to look for certificates with notBefore >= 2nd November 2014 that chain to publicly trusted roots and include any Internal Names or Reserved IP Addresses," he wrote. "We found non-compliant certificates issued by quite a number of other CAs, but I'll document these in another post."

One of the key weaknesses with the current Web-encryption system built on the transport layer security protocol is that it has too many single points of failure. It's reassuring to see Comodo monitoring its certificate issuance process to make sure it complies with rules aimed at securing the entire Internet. The transparency and accountability shown by Comodo is in sharp contrast to competing CA Symantec, which recently was publicly chastised by developers of Google's Chrome browser for several HTTPS certificate mishaps.