New firmware for Siemens 35 and 45 Series to fix SMS freeze fault.

Users of Siemens 35 and 45 series phones have been warned of a bug which allows the handsets to be disabled by an incoming text message.

The fault is linked to the enhanced messaging service technology in the phones. A correctly formatted incoming message can freeze the 35 series phone immediately and cause the 45 series to hang for up to two minutes. To activate the flaw, the message would need to contain a single word from the phone's language menu, preceded by a special character and surrounded by quotes, such as "%English" or "%Deutsch."

Siemens has been aware of the bug for some time but PC World reports that the company did not publicise the flaw in case attackers exploited it.

The Siemens flaw follows a glitch discovered last month in the Nokia 6210, which was also found to be susceptible to Denial of Service attacks. A vulnerability could let an attacker use the phone's VCard attachments facility to reboot or disable the handset.

Nokia said it did not intend release a patch for that vulnerability, as chances for its exploitation were considered remote. The Nokia flaw was discovered by US company @Stake, which said the bug illustrated the need for new mobile phone features to be thoroughly tested and debugged before introduction.