A threat actor using the handle “zeroplayer” advertised a previously unknown remote-code-execution (RCE) exploit for WinRAR on an underground forum.

According to ThreatMon, the post, titled “WINRAR RCE 0DAY – 80,000$,” claims the flaw works “fully on the latest version of WinRAR and below,” is not related to the recently patched CVE-2025-6218, and is available exclusively through the forum’s escrow (“Garant”) service for USD 80,000.

Key Takeaways
1. Threat actor "zeroplayer" is selling a WinRAR RCE exploit on dark web forums for  $80,000, distinct from CVE-2025-6218 and affecting latest versions.
2. WinRAR's installation on hundreds of millions of Windows systems creates widespread vulnerability through malicious archive attachments.
3. APT groups and crimeware operators could weaponize the exploit to compress attack timelines from weeks to hours via email campaigns.
4. Organizations should temporarily use 7-Zip alternatives, deploy sandbox detonation, and enable Attack Surface Reduction while awaiting RARLAB's patch.

The disclosure underscores the enduring appeal of WinRAR—a utility installed on hundreds of millions of Windows endpoints—as a high-value target for cyber-criminals.

Critical WinRAR Exploit Threatens Enterprises

While zeroplayer has held proof-of-concept (PoC) details, previous WinRAR RCE chains provide insight into potential exploitation paths.

Historically, attackers abuse WinRAR’s file-format parsing logic especially within UNACEV2.dll or crafted .RAR / .ZIP archives—to trigger memory corruption. A typical exploit flow involves:

Archive Crafting – An attacker embeds malformed headers or over-long filenames (0x414141…) to corrupt the stack or heap.
Payload Staging – A small shellcode stub sets EIP to a controlled address, then downloads a larger payload.
Privilege Escalation / Persistence – Attackers often drop binaries to %AppData%\\Roaming\\Microsoft\\Windows\\Start Menu\\Programs\\Startup\\ to auto-execute at logon, or leverage COM hijacking keys like HKCU\\Software\\Classes\\mscfile\\Shell\\Open\\Command.

If zeroplayer’s exploit bypasses WinRAR’s current DEP/ASLR mitigations, it could enable reliable code-execution on fully patched Windows 11 systems with default settings—a nightmare scenario for defenders.

WinRAR’s ubiquity in enterprises, combined with routine email use of compressed attachments, offers a near-frictionless delivery channel for threat actors.

Notably, APT groups such as APT40 and Sandworm previously chained WinRAR parsing flaws to deploy DarkMe, BitterRAT, and UAC-0050 implants during spear-phishing campaigns. A viable zero-day at an $80 k price point therefore presents:

Crimeware-as-a-Service (CaaS) brokers could weaponize the bug into maldoc-style lures, similar to CVE-2019-0969 campaigns.
Software build servers that automatically unpack third-party archives are prime secondary targets.
Initial-access brokers might purchase the exploit, establish footholds, and then auction access to ransomware affiliates, compressing dwell time from weeks to hours.

Security teams should monitor for anomalous archive extraction behavior, deploy virtual patching via intrusion-prevention signatures, and prepare for out-of-cycle vendor updates. Until a fix arrives, cyber-hygiene around untrusted archives remains paramount.

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