CVE-2015-7645

What Is Adobe Flash Player?

Adobe Flash Player was the ubiquitous cross-platform multimedia browser plugin, installed on over 90% of internet-connected computers at peak deployment. Flash's universal presence made every Flash vulnerability a potential attack vector against virtually any Windows, macOS, or Linux system with a browser. Adobe ended Flash Player support December 31, 2020.

Overview

CVE-2015-7645 is a Flash Player zero-day used by APT29 (also tracked as Cozy Bear, Pawn Storm, and associated with Russia's SVR intelligence service) in targeted spear-phishing attacks against U.S. government targets in October 2015. Trend Micro detected the campaign and notified Adobe; Adobe released an emergency out-of-band patch APSB15-27 on October 16, 2015. The vulnerability was also used by ransomware operators, earning ransomwareUse: true status. The CVSS AV:L (local attack vector) reflects that the exploit was delivered via an embedded Flash file in an email attachment or document — requiring the user to open the file locally — rather than via a web-based drive-by attack.

Affected Versions

Technical Details

Root Cause: Flash Memory Corruption (Out-of-Bounds Write)

CVE-2015-7645 involves a memory corruption flaw (CWE-787, out-of-bounds write) in Adobe Flash Player's handling of a crafted SWF file. The exploit is triggered when Flash processes specific SWF content — either embedded in an email attachment or loaded from a web page — causing Flash to write beyond the bounds of a heap-allocated buffer.

The AV:L CVSS attack vector for this vulnerability reflects the primary delivery mechanism observed in the wild: APT29 embedded malicious Flash content in spear-phishing email attachments (Office documents containing embedded SWF files, or direct SWF attachments) rather than relying solely on browser-based drive-by delivery. When the target opens the attachment, Flash renders the embedded content and triggers the exploit.

Exploitation follows the standard Flash memory corruption pattern:

1. Heap grooming — shape Flash's heap to control adjacent allocation positions
2. Out-of-bounds write trigger — the crafted SWF triggers the overflow into adjacent heap data
3. Control flow hijacking — overwrite a function pointer or vtable pointer
4. ASLR bypass — use an information leak or heap spray for reliable addressing
5. Code execution — execute shellcode or a ROP chain to launch the payload

APT29 Targeting

APT29 (Cozy Bear) is attributed to Russia's SVR (Foreign Intelligence Service) and focuses on espionage targeting governments, think tanks, NGOs, and defense contractors. In October 2015, Trend Micro observed APT29 deploying CVE-2015-7645 in a targeted campaign against U.S. government organizations and defense contractors — consistent with the group's established focus on U.S. foreign policy and defense intelligence.

Ransomware Use

In addition to APT29's targeted espionage use, CVE-2015-7645 was incorporated into ransomware delivery campaigns — demonstrating that high-profile Flash zero-days are quickly adopted by both nation-state actors (for targeted exploitation) and criminal operators (for mass monetization).

Attack Characteristics

Discovery

Trend Micro's Pawn Storm research team discovered CVE-2015-7645 while tracking APT29's October 2015 campaign. Adobe received notification on approximately October 14 and released APSB15-27 on October 16, 2015.

Exploitation Context

• APT29 espionage campaign: APT29 used CVE-2015-7645 in a targeted spear-phishing campaign against U.S. government organizations in October 2015; this campaign contributed to broader intelligence about Russian espionage activities targeting U.S. institutions during the 2015–2016 period
• Ransomware delivery (confirmed): CVE-2015-7645 was also used by criminal ransomware operators as a Flash-based delivery vehicle; the ransomwareUse flag confirms independent criminal adoption of the same zero-day exploit
• Flash zero-day eighth in 2015: CVE-2015-7645 was the eighth Flash zero-day of 2015 — following CVE-2015-0311, CVE-2015-0313, CVE-2015-3043, CVE-2015-3113, CVE-2015-5119, CVE-2015-5122, and CVE-2015-5122 — cementing 2015 as the worst year in Flash's history for zero-day exploitation
• Flash EOL legacy: Flash is permanently end-of-life since December 2020; all known Flash vulnerabilities remain permanently unpatched
• CISA KEV (2022): Added March 2022

Remediation

1. Remove Flash Player — uninstall from all systems. Adobe's Flash uninstaller and Microsoft's KB4577586 (Windows Update) remove Flash from Windows. Flash is permanently end-of-life with no further security updates.

2. Migrate Flash-dependent applications — identify remaining Flash content (internal apps, kiosks, ICS HMIs) and migrate to HTML5 or another supported technology.

3. Network isolation — Flash-dependent systems that cannot be decommissioned should be isolated from internet access and untrusted networks.

4. Block Flash content in email — even for systems that must retain Flash, configure email security gateways to block SWF files and Office documents with embedded SWF content to eliminate the attachment delivery vector used by APT29.

5. Browser controls — all modern browsers have removed Flash support. IE11 with Flash (if still present) should be upgraded to Edge or Chrome.