Colin Mc Hugo

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Colin Mc Hugo
Security Engineer Manager & CEO at Quantum Infinite Solutions Group Ltd.

Linphone SIP Stack Bug Could Let Attackers Remotely Crash Client Devices

September 1, 2021

Cybersecurity researchers on Tuesday disclosed particulars a couple of zero-click safety vulnerability in Linphone Session Initiation Protocol (SIP) stack that might be remotely exploited with none motion from a sufferer to crash the SIP consumer and trigger a denial-of-service (DoS) situation.

Tracked as CVE-2021-33056 (CVSS rating: 7.5), the difficulty considerations a NULL pointer dereference vulnerability within the “belle-sip” element, a C-language library used to implement SIP transport, transaction, and dialog layers, with all variations previous to 4.5.20 affected by the flaw. The weak spot was found and reported by industrial cybersecurity firm Claroty.

Linphone is an open-source and cross-platform SIP consumer with help for voice and video calls, end-to-end encrypted messaging, and audio convention calls, amongst others. SIP, however, is a signaling protocol used for initiating, sustaining, and terminating real-time multimedia communication periods for voice, video, and messaging functions over the web.

To that finish, the remotely exploitable vulnerability may be activated by including a malicious ahead slash (“To (the decision recipient), From (initiator of the decision), or Diversion (redirect the vacation spot endpoint), leading to a crash of the SIP consumer software that makes use of the belle-sip library to deal with and parse SIP messages.

“The underlying bug right here is that non-SIP URIs are accepted as legitimate SIP header values,” Claroty researcher Sharon Brizinov said in a write-up. “Subsequently, a generic URI corresponding to a easy single ahead slash shall be thought of a SIP URI. Which means that the given URI won’t include a sound SIP scheme (scheme shall be NULL), and so when the [string] evaluate perform known as with the non-existent scheme (NULL), a null pointer dereference shall be triggered and crash the SIP consumer.”

It is value noting that the flaw can also be a zero-click vulnerability because it’s potential to trigger the SIP consumer to crash just by sending an INVITE SIP request with a specially-crafted From/To/Diversion header. As a consequence, any software that makes use of belle-sip to research SIP messages shall be rendered unavailable upon receiving a malicious SIP “name.”

Though the patches can be found for the core protocol stack, it is important that the updates are utilized downstream by distributors that depend on the affected SIP stack of their merchandise.

“Profitable exploits focusing on IoT vulnerabilities have demonstrated they’ll present an efficient foothold onto enterprise networks,” Brizinov mentioned. “A flaw in a foundational protocol such because the SIP stack in VoIP telephones and functions may be particularly troublesome given the dimensions and attain proven by assaults in opposition to quite a few different third-party elements utilized by builders in software program tasks.”

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