Adobe Issues Emergency Patch for Flash Zero-Day

Adobe has released security updates to patch vulnerabilities in Adobe Flash Player for Windows, Mac, Linux, and Chrome OS. The fixes for CVE-2018-4945, CVE-2018-5000, CVE-2018-5001, and CVE-2018-5002 all address critical vulnerabilities in version 29.0.0.171 and earlier.

CVE-2018-4945, a type confusion vulnerability, and CVE-2018-5002, a stack-based buffer overflow vulnerability, both enable arbitrary code execution. CVE-2018-5000 and CVE-2018-5001 enable information disclosure. All are patched in Adobe Flash version 30.0.0.113.

CVE-2018-5002 was discovered being used in limited, targeted attacks on Windows users in the wild, Adobe reports. The exploit uses an Office document to download and execute an Adobe Flash exploit to target machines, according to the Icebrg Security Research Team, one of a few organizations to independently identify and report the vulnerability to Adobe.

Attacks arrive as emails with attached Microsoft Office documents containing embedded malicious Flash Player content. The attack loads Adobe Flash from within Microsoft Office, a common approach to Flash exploitation since most people have Flash disabled in the browser. An embedded Flash file in the document might contain the full exploit or set the stage for the attack to selectively download exploits and payloads.

Unlike similar attacks, this one uses the lesser-known tactic of remotely including Flash content instead of embedding it within the document, Icebrg researchers explain. This means the document does not contain malicious code and therefore won't raise any red flags. Further, because attackers can choose which exploits to use on a recipient, they can choose their victims.

Researchers suggest the attack might be targeting victims in Qatar, a finding based on the weaponized document, which is written in Arabic and appears to contain information on salary changes. The file was uploaded to VirusTotal from an IP address in Qatar earlier this year, and many of the job titles specifically refer to secretaries, ambassadors, and diplomats.

Icebrg points to a few key indicators that could suggest a machine is under attack. Alone, these might not indicate a threat, but multiple indicators could suggest malicious activity. Signs include the use of newly registered domains and low-reputation infrastructure (they use provider Abelons as an example), staged downloads of Flash, a newly observed "Let's Encrypt" certificate from a free provider, and Office documents embedding Flash using remote inclusion.

Microsoft published security advisory notification 180014 and released an update in response to the fixes. US-CERT also issued an advisory on Adobe's security updates. The National Cybersecurity and Communications Integration Center (NCCIC) advises users and administrators to review Adobe's security advisory and apply all necessary updates.

CVE-2018-5002 was independently reported by Icebrg.io, members of 350 Threat Intelligence Center at 360 Enterprise Security Group, and members of the Qihoo 360 Core Security Group. CVE-2018-4945 was discovered by experts at Tencent KeenLab and Trend Microsoft's Zero Day Initiative. CVE-2018-5000 and CVE-2018-5001 were both reported via Trend Micro's ZDI.

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