Rewterz Threat Advisory – PDF documents that exploit unpatched flaw in Chrome to harvest user data

Severity

Medium

Analysis Summary

Multiple PDF samples are discovered in the wild which exploit a Google Chrome unpatched flaw. The exploited vulnerability allows the sender of the PDF files to track the users and collect some user information when they use Google Chrome as a local PDF viewer.

These samples acted alright in the local PDF viewer but made suspicious outbound traffic when they were opened locally on Google Chrome.

Researchers observed that data was being sent to readnotify[.]com without informing user. The traffic is a HTTP POST packet, according to which following information of the user may be collected by the malicious sender:

1. The public IP address of the user.
2. OS, Chrome version etc. (in HTTP POST header).
3. The full path of the PDF file on user’s computer (in HTTP POST payload).

This affects Google Chrome (as local PDF viewer), not Adobe Reader and does not allow NTLM stealing, but it leaks your OS information and the path of the file stored on your local disk.

Another PDF sample cpmmunicated with hxxp[:]//zuxjk0dftoamimorjl9dfhr44vap3fr7ovgi76w[.]burpcollaborator[.]net

Impact

Personal Information Disclosure

Affected Products

Google Chrome

Indicators of Compromise

IP(s) / Hostname(s)

zuxjk0dftoamimorjl9dfhr44vap3fr7ovgi76w[.]burpcollaborator[.]net

52[.]16[.]21[.]24

91[.]103[.]1[.]84

URLs

hxxp[:]//zuxjk0dftoamimorjl9dfhr44vap3fr7ovgi76w[.]burpcollaborator[.]net

readnotify[.]com

Filename

• honduras-bginfo.pdf
• hond-la-moskitia.pdf
• minimal.pdf
• western-honduras.pdf
• honduras-directory.pdf
• central-honduras.pdf
• hond-tegucigalpa.pdf
• honduras-the-bay-islands-health.pdf
• honduras-bginfo.pdf

Malware Hash (MD5/SHA1/SH256)

• 2dd6ade4d0d4dc8224b28f8819b1c49bb7ae4025933e737ac8069c496d88bb43
• 286ed6d0261aed1115e06e2e8cf0af840297241e9dc9494a496a2c8b75457749
• 58959ac247caf322c800616f3526828d
• 19ac1c943d8d9e7b71404b29ac15f37cd230a463003445b47441dc443d616afd
• d949720af989e5e492570f0918362867
• a21a4fcc75cd20a0965f1673b98c0dd688711c40cbabf92a5e5cd1f31a7ac684
• 4eb84fee8e92685b6a789f1af5c732c7
• 1d151793f521419c1470079a37b1e37b8b59a5b69a5506f1d0dbee6f3995b25d
• 6cfddeaf454995a0d6038363231f69a3
• 0c3e8efd667f7ff1549bfd2a4498105cb2607314d73b7105f4c1d747d7341090
• aa7a1c701e99f345b0e37aa52f895b79
• fb56efe75f3b4509d5a2e0655536d9dab121798d92b8660121bd4691265a87e3
• c82dcf3998782306d71b1f360cc3f8a1
• 622624d6f161b7d2fa7859d46792dd6bb49024b432b04106b1818510a2037689
• e1ae5658b61972bd173b669b8b6931dd
• 0cc1234c981806dd22e0e98e4be002e8df8d285b055e7f891ff8e91af59aee1e
• 54ff8899c86142bdf2dde6468ca17750
• 13090c4e8338fa2769a29356de72b306
• 2dd6ade4d0d4dc8224b28f8819b1c49bb7ae4025933e737ac8069c496d88bb43
• 286ed6d0261aed1115e06e2e8cf0af840297241e9dc9494a496a2c8b75457749
• 58959ac247caf322c800616f3526828d
• 19ac1c943d8d9e7b71404b29ac15f37cd230a463003445b47441dc443d616afd
• d949720af989e5e492570f0918362867
• a21a4fcc75cd20a0965f1673b98c0dd688711c40cbabf92a5e5cd1f31a7ac684
• 4eb84fee8e92685b6a789f1af5c732c7
• 1d151793f521419c1470079a37b1e37b8b59a5b69a5506f1d0dbee6f3995b25d
• 6cfddeaf454995a0d6038363231f69a3
• 0c3e8efd667f7ff1549bfd2a4498105cb2607314d73b7105f4c1d747d7341090
• aa7a1c701e99f345b0e37aa52f895b79
• fb56efe75f3b4509d5a2e0655536d9dab121798d92b8660121bd4691265a87e3
• c82dcf3998782306d71b1f360cc3f8a1
• 622624d6f161b7d2fa7859d46792dd6bb49024b432b04106b1818510a2037689
• e1ae5658b61972bd173b669b8b6931dd
• 0cc1234c981806dd22e0e98e4be002e8df8d285b055e7f891ff8e91af59aee1e
• 54ff8899c86142bdf2dde6468ca17750
• 13090c4e8338fa2769a29356de72b30

Remediation

• Block the threat indicators at their respective controls.
• Use alternative PDF reader application for viewing received PDF documents locally until Chrome fixes the issue, or disconnect computer from the Internet when opening PDF documents in Chrome.