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Threat Brief: OWASSRF Vulnerability Exploitation
Unit 42 details active exploitation of Exchange SSRF flaws CVE-2022-41080/CVE-2022-41082 via the OWASSRF method, deploying the SilverArrow PowerShell backdoor.
Unit 42 documents OWASSRF, an exploit chain combining CVE-2022-41080 and CVE-2022-41082 to achieve remote code execution on Microsoft Exchange via Outlook Web Access, bypassing Microsoft's ProxyNotShell mitigations. Active exploitation was observed in late November and early December 2022, affecting at least eight organizations. Attackers authenticated to Exchange, then executed a PowerShell backdoor tracked as SilverArrow to create admin accounts, install AnyDesk, tunnel RDP via PuTTY Link, and dump LSASS memory for credential theft. Exploitation is isolated rather than mass-scale because authentication is required.
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CVE-2026-81578 + CVE-2026-82078 | PaperCut NG/MF Authentication Bypass and Unsafe Dynamic Class Loading Vulnerabilities
Two chained PaperCut NG/MF flaws, CVE-2026-81578 and CVE-2026-82078, enable pre-auth RCE, with active exploitation confirmed in customer environments.
PaperCut NG/MF is affected by CVE-2026-81578, an improper access control flaw (CVSS 4.0 8.8) allowing unauthenticated configuration changes, and CVE-2026-82078, an unsafe dynamic class loading flaw (CVSS 4.0 9.4) enabling arbitrary Java bytecode execution. Chained, they yield pre-authentication remote code execution on the PaperCut Application Server. PaperCut confirmed active exploitation and customer incidents, and Huntress observed exploitation starting August 26, 2026. Emergency Patch Release 2 is available for NG/MF v24-v26, with IOCs including suspicious pc-app.exe child processes, truncated server.log files, and AnyDesk installs.
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U.S. CISA adds MRLG, PHPMailer, Rails Ruby on Rails, and Synacor Zimbra Collaboration Suite flaws to its Known Exploited Vulnerabilities catalog
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Almost a Fifth of Global Firms Targeted with Spring4Shell
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iCagenda and Balbooa Forms Joomla Flaws Reportedly Exploited as Zero
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CISA Adds Six Exploited Flaws to KEV, Including NetScaler, Linux, and SQL Server Bugs
CISA added six actively exploited flaws to KEV, led by Citrix NetScaler CVE-2026-8452, with federal patch deadlines set.
CISA added six flaws to the KEV catalog on August 27, 2026, citing evidence of active exploitation, led by CVE-2026-8452, an improper buffer restriction in Citrix NetScaler ADC and Gateway that can cause denial-of-service. Defused Cyber and Previdian reported active exploitation of CVE-2026-8452, with 36 attempts over 12 days from 12 attacker IPs deploying web shells x.php and z.php. The other additions cover SQL Server RCE (CVE-2019-1068), Linux kernel out-of-bounds write (CVE-2022-0995), Red Hat ABRT and libuser privilege escalations (CVE-2015-5287, CVE-2015-3246), and AjaxPro deserialization RCE (CVE-2021-23758). FCEB agencies must patch CVE-2019-1068 and CVE-2026-8452 by August 29, 2026, and the rest by September 9, 2026.
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Critical Issabel PBX Command Execution Vulnerability Exploited in the Wild
Unauthenticated attackers exploit CVE-2026-89026 in Issabel PBX via forged JWT tokens to run OS commands; exploitation observed since September 9.
CVE-2026-89026 (CVSS v4 9.3) stems from a hard-coded HS256 JWT signing key in Issabel Framework's pbxapi/index.php, letting unauthenticated attackers forge bearer tokens and execute OS commands through the Asterisk Manager Interface originate endpoint. Issabel Framework versions before commit b97dbaf0b71c1c36f841e672b664afbeb02773bd are affected. Shadowserver Foundation first observed exploitation on September 9, 2026, and VulnCheck added the flaw to its Known Exploited Vulnerabilities database.
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