VulnerabilityBleeping Computer
6.1 — HIGH
Russian hackers exploit Exchange OWA zero-day for long-term mailbox access
The Russian state-sponsored hacking group Laundry Bear, also known as Void Blizzard, is exploiting an Exchange Outlook Web Access vulnerability in email campaigns to deliver a sophisticated backdoor called OWAReaper. [...]
🤖 AI BriefingAuto-generated threat analysis
🔍Threat Overview
Russian state-sponsored hacking group Laundry Bear (TA488) is exploiting a zero-day vulnerability in Microsoft Exchange Server's Outlook Web Access to deliver a sophisticated backdoor called OWAReaper, allowing long-term access to targeted mailboxes.
⚙️Technical Details
CVEs
CVE-2026-42897CVE-2025-66376
Affected Systems
Microsoft Exchange ServerSynacor Zimbra Collaboration Suite
Attack Vectors
NETWORK
💥Impact Assessment
Severity: high
🛡️Recommended Actions
1Implement a web application firewall (WAF) to block malicious traffic
2Regularly update Microsoft Exchange Server to patch CVE-2026-42897
3Monitor mailboxes for suspicious activity and implement two-factor authentication
📦Affected Products
Microsoft Exchange ServerMicrosoft Exchange Server Subscription EditionSynacor Zimbra Collaboration Suite
🔐NVD Verified DataVERIFIED
CVE-2026-42897 ↗CVSS 6.1 — MEDIUM
Attack Vector
NETWORK
Complexity
LOW
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:NWeaknesses
CWE-79
Affected Products (CPE)
Microsoft Exchange ServerMicrosoft Exchange Server Subscription Edition
CVE-2025-66376 ↗CVSS 6.1 — MEDIUM
Attack Vector
NETWORK
Complexity
LOW
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:NWeaknesses
CWE-79
Affected Products (CPE)
Synacor Zimbra Collaboration Suite
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