Re: [Full-disclosure] Cisco Phone 7940 remote DOS

Hello -

This is Cisco's response to the message posted by Radu State to full- disclosure on Wednesday Dec 5 2007. Cisco greatly appreciates the opportunity to work with researchers on security vulnerabilities, and welcomes the opportunity to review and assist in product reports.

Cisco confirms that there is an issue whereby a crafted sequence of SIP messages may cause the phone to enter a state where no calls can be placed from, or received by a Cisco IP phone running Session Initiation Protocol (SIP) software. Once the crafted SIP messages stop, the device will return to normal service. This issue is tracked by Cisco bug ID CSCsl63427. Registered customers will be able to view additional information here method=fetchBugDetails&bugId=CSCsl63427

This issue is not seen when the SIP phone is registered to a Cisco Unified Communications Manager (CUCM) server, as additional checking is done that would prevent the attack.

Cisco was unable to reproduce the device restart as described by Mr. State.

This issue has been assigned the Common Vulnerabilities and Exposures identifier of CVE-2007-5583.

As a possible mitigation for this issue, Cisco recommends, as a best practice, that voice infrastructure devices are kept on separate
networks from data devices. In this case, the crafted packets may be prevented from reaching the
voice devices.


Clay Seaman-Kossmeyer

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