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Attackers Chain Two PaperCut Flaws to Execute Code Without Authentication
Attackers chain PaperCut NG/MF flaws CVE-2026-81578 and CVE-2026-82078 for unauthenticated RCE; exploitation observed and a second emergency patch issued.
Two flaws in PaperCut NG and MF — CVE-2026-81578 (CVSS 8.8, improper access control enabling auth bypass) and CVE-2026-82078 (CVSS 9.4, unsafe dynamic class loading) — are being chained for unauthenticated remote code execution. Huntress observed limited exploitation on two customer environments, including Base64-encoded commands, 'whoami & ver' fingerprinting, SimpleHelp execution, and AnyDesk installation for persistence. PaperCut released a second emergency patch for v24, v25, and v26, but watchTowr reports additional patch bypasses may still affect the latest version. Shared IoCs include crafted jdbc strings in server.log and attacker-written .class/.cmd files.
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Microsoft Fixes Windows Defender Zero
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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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Threat Brief: Atlassian Confluence Remote Code Execution Vulnerability (CVE-2022
Unauthenticated Confluence RCE CVE-2022-26134 was exploited in the wild; Volexity observed intrusions and Cerber ransomware on unpatched servers.
Volexity identified exploitation of CVE-2022-26134, an unauthenticated remote code execution vulnerability in Atlassian Confluence Server and Data Center, during Memorial Day weekend 2022, with Atlassian issuing a patch. Cortex Xpanse found 19,707 potentially affected Confluence instances, concentrated in the US, Germany, China, and Russia, plus 1,251 end-of-life versions exposed. Unit 42 and Cortex Managed Threat Hunting observed successful exploitation leading to reconnaissance commands and a Cerber ransomware deployment that was blocked by Cortex XDR. A public PoC has increased exploitation risk.
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Acronis backup plugin flaw exploited in targeted attacks (CVE-2026-87886)
Acronis warns CVE-2026-87886, an authenticated Linux privilege escalation flaw in its cPanel, WHM, and Plesk backup plugins, is under limited targeted exploitation; patches released.
Acronis disclosed CVE-2026-87886, a privilege escalation vulnerability caused by insecure file permissions in its backup plugins for cPanel, WHM, and Plesk, platforms popular among hosting providers and MSPs. Exploitation has been detected in the wild in limited, targeted attacks against cPanel & WHM deployments, with no exploitation observed on Plesk so far, and the low-complexity attack requires no user interaction. Fixes shipped last week: backup plugin version 1.9.3 HF3 for cPanel & WHM and extension version 1.8.11 for Plesk.
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Microsoft fixes actively exploited zero-days (CVE-2024-43451, CVE-2024-49039)
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CISA Warns of Critical ScreenConnect Vulnerability Actively Exploited in Attacks
CISA added actively exploited ConnectWise ScreenConnect flaw CVE-2026-84869 to the KEV catalog, setting a September 14 patch deadline.
CISA added CVE-2026-84869, a critical improper privilege management and missing authorization flaw (CWE-269, CWE-862) in ConnectWise ScreenConnect, to its Known Exploited Vulnerabilities Catalog on September 11, 2026, confirming active exploitation. The flaw lets attackers transfer files to a device and execute them during an active remote ScreenConnect session without authorization or host-user confirmation, enabling payload delivery, unauthorized tools, and persistence while blending into legitimate remote-management traffic. CISA set a September 14 remediation deadline under BOD 26-04 and flagged the vulnerability as requiring forensic triage. ConnectWise has published a security bulletin, and defenders are urged to review exposure, sessions, file-transfer records, and outbound connections.
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U.S. CISA adds Ivanti EPMM, MDaemon Email Server, Srimax Output Messenger, Zimbra Collaboration, and ZKTeco BioTime flaws to its Known Exploited Vulnerabilities catalog
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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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Off Guard: Breaking LiteLLM from authentication bypass to cloud compromise
Wiz found LiteLLM auth bypass (CVE-2026-59822) and post-auth RCE (CVE-2026-59821) chainable to cloud compromise; the bypass is in CISA KEV with in-the-wild exploitation.
Wiz scanned roughly 3,074 internet-facing LiteLLM deployments and found 9.6% accepted the default master key sk-1234 or required no authentication, making post-auth attacks effectively pre-auth. The MCP endpoint accepts any Bearer token and grants a valid session (CVE-2026-59822), confirmed exploited in the wild via honeypots and added to CISA's Known Exploited Vulnerabilities catalog. Custom code guardrails allow post-auth root-level RCE via exec(compile(...)) (CVE-2026-59821), while pass-through endpoints lack URL validation, enabling cloud credential theft in post-auth scenarios. All assigned vulnerabilities have been patched; the research was presented at DEF CON 34.
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Weekly Cybersecurity Newsletter Bulletin – Microsoft 0-day, FortiOS, PAN-OS Flaw, Revolut Data Breach, and 20+ Stories
Weekly roundup: Microsoft patches 973 flaws including two actively exploited zero-days; FortiOS CAPWAP flaw deploys PivotC2 RAT; PAN-OS root RCE disclosed.
Microsoft's September 2026 Patch Tuesday fixed 973 vulnerabilities, including two zero-days under active exploitation: CVE-2026-85880 (Windows ALPC) and CVE-2026-81963 (Windows Update Stack), both elevation-of-privilege bugs. SOCRadar reported active exploitation of CVE-2025-25249 (CVSS 9.8) in FortiOS CAPWAP, deploying a Node.js RAT called PivotC2 that exfiltrates Exchange mailboxes to Wasabi cloud storage; 178 devices were compromised out of 30,000 scanned IPs, attributed to a Russian-speaking financially motivated group. Palo Alto disclosed CVE-2026-0310, a 9.2-rated buffer overflow enabling root code execution on PA-Series firewalls, and Fortinet disclosed CVE-2026-84393, a ZTNA certificate validation MITM flaw. Cyera also revealed CVE-2026-6471 ('PostGREShell'), a 12-year-old PostgreSQL logical-decoding flaw allowing code execution via REPLICATION-privileged accounts.
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