Cisco has advised users to update the firmware on some of its IP phones following the discovery of two security flaws.

A brace of Session Initiation Protocol (SIP) vulnerabilities in Cisco 7940/7960 IP Phones create the potential for hackers to crash - but not to run exploit code - on vulnerable handsets.

SIP is a signalling protocol for VoIP. The protocol can be used to create two-party, multiparty, or multicast sessions.

Cisco IP Phone 7940/7960 SIP firmware versions prior to 8.7(0) are vulnerable to the denial of service attacks, Cisco warns. Users are advised to update their firmware to version 8.7(0), as explained in its advisory here.

More detail on the vulnerabilities can be found in posts (here and here) to full disclosure mailing lists by the independent security researchers (Radu State, Humberto J Abdelnur, and Olivier Festor) who discovered the bugs. ®

Related stories

• Cisco VoIP bug poses eavesdropping risk (29 November 2007)

  https://www.theregister.com/2007/11/29/cisco_voip_bug/

• Cisco WiMAX acquisition rumors resurface (3 October 2007)

  https://www.theregister.com/2007/10/03/cisco_wimax_acquisition/

• Cisco patches serious holes in voice-enabled offerings (8 August 2007)

  https://www.theregister.com/2007/08/08/cisco_issues_four_updates/

• Cisco wraps up against VoIP DoS bugs (29 March 2007)

  https://www.theregister.com/2007/03/29/cisco_voip_dos_bug_fix/

• Apple and Cisco kiss and make up (22 February 2007)

  https://www.theregister.com/2007/02/22/iphone_to_be_shared/

• Cisco aims to plug channel knowledge gap on VoIP (28 November 2006)

  https://www.theregister.com/2006/11/28/cisco_channel_prgrammes/

• Cisco gains patent on 'triple play' (16 October 2006)

  https://www.theregister.com/2006/10/16/cisco_triple_threat/