Vulnerability Note VU#155412
Samsung Galaxy S phones fail to properly validate SwiftKey language pack updates
Original Release date: 16 Jun 2015 | Last revised: 25 Jun 2015

Overview
Samsung Galaxy S phones, including the S4 Mini, S4, S5, and S6, fail to properly validate Swiftkey language pack updates.

Description
CWE-345: Insufficient Verification of Data Authenticity – CVE-2015-4640
Samsung Galaxy S phones, including the S4 Mini, S4, S5, and S6, are pre-installed with a version of SwiftKey keyboard that is signed by Samsung to operate with system privileges. By design, SwiftKey periodically checks for language pack updates over HTTP (CVE-2015-4640). By intercepting such requests and modifying the necessary fields, an attacker can write arbitrary data to vulnerable devices.

SwiftKey has stated that the "vulnerability is unrelated to and does not affect our SwiftKey consumer apps on Google Play and the Apple App Store."

Impact
A remote, unauthenticated attacker conducting a man-in-the-middle attack may be able to write arbitrary data to vulnerable devices checking for updates. Based on the frequency of SwiftKey update checks, which "appears to be every 8 hours" according to NowSecure researchers, such an attack may have a low likelihood of occurring.

Solution
Apply an update

Samsung has provided a firmware update to cell phone carriers for distribution to affected users. If your cell phone carrier has not provided the over-the-air update, consider the following workaround:
Avoid untrusted networks

Avoid using untrusted networks, including public WiFi. Using your device on an untrusted network increases the chance of falling victim to a MITM attack.

Vendor Information (Learn More)

VendorStatusDate NotifiedDate UpdatedSamsungAffected02 Mar 201516 Jun 2015If you are a vendor and your product is affected, let
us know.

CVSS Metrics (Learn More)

Group
Score
Vector

Base
5.7
AV:A/AC:M/Au:N/C:N/I:C/A:N

Temporal
4.5
E:POC/RL:OF/RC:C

Environmental
4.5
CDP:N/TD:H/CR:ND/IR:ND/AR:ND

References

https://www.nowsecure.com/blog/2015/06/23/on-detecting-and-preventing-the-samsung-ime-keyboard-swiftkey-language-pack-update-vulnerability/

Remote Code Execution as System User on Samsung Phones


http://global.samsungtomorrow.com/information-regarding-the-keyboard-security-issue-and-our-device-policy-update/
http://swiftkey.com/en/blog/samsung-keyboard-security-vulnerability-swiftkey/
http://arstechnica.com/security/2015/06/new-exploit-turns-samsung-galaxy-phones-into-remote-bugging-devices/
https://www.blackhat.com/ldn-15/summit.html#abusing-android-apps-and-gaining-remote-code-execution
http://cwe.mitre.org/data/definitions/300.html

Credit

Thanks to Ryan Welton and Ted Eull of NowSecure for reporting this vulnerability.
This document was written by Joel Land.

Other Information

CVE IDs:
CVE-2015-4640
CVE-2015-4641

Date Public:
16 Jun 2015

Date First Published:
16 Jun 2015

Date Last Updated:
25 Jun 2015

Document Revision:
32

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