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Secure phone app library vulnerable

SilentCircle, others need upgrades

Users of a number of telephone apps need to upgrade, with a security researcher publishing research identifying serious vulnerabilities in ZRTPCCP, a core security library.

As ThreatPost notes, the compromised library counts PGP luminary Phil Zimmerman's SilentCircle secure comms application among its users.

Researcher Mark Dowd of Azimuth Security identified a variety of bugs including a remote heap overflow, a number of stack overflows, and information leakage.

The flaws exist in the GNU ZRTPCPP library. As well as SilentCircle, the library is used in LinPhone, CsipSimple, Twinkle, various Ostel clients, and “anything using the GNU ccRTP with ZRTP enabled”, Dowd writes.

The Zimmerman-designed ZRTP protocol is implemented in the library as part of the GNU secure telephony stack. It works by using an established RTP session to establish a cryptographically-protected authenticated session.

The first vulnerability exists in the Zrtp::storeMsgTemp() function, which can be crashed remotely by sending an over-sized packet, “leading to potential arbitrary code execution on the vulnerable host”.

The second vulnerability he identified is a number of functions that can be crashed with a remote heap overflow. However, Dowd was unsure as to whether this gave rise to an exploitable condition.

Finally, the library fails to validate whether a packet is of the expected size. “This can lead to both information leaking and out of bounds data reads (usually resulting in a crash)”, Dowd writes.

The good news is that the library has been updated in github, and a SilentCircle update is available in both the Android and Apple versions (via Google Play and the AppStore). ®

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