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Microsoft SharePoint servers under attack via zero-day vulnerability (CVE-2025-53770)
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Critical Unpatched SharePoint Zero-Day Actively Exploited, Breaches 75+ Company Servers
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U.S. CISA urges to immediately patch Microsoft SharePoint flaw adding it to its Known Exploited Vulnerabilities catalog
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Microsoft patches actively exploited Exchange, Excel zero-days (CVE-2021-42321, CVE-2021-42292)
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Microsoft Releases Fix for Zero-Day Flaw in July 2022 Security Patch Rollout
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May 2026 CVE Landscape
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Critical N-able N-central Vulnerability and Active Exploitation
N-able N-central pre-auth RCE zero-day CVE-2026-86218 (CVSS 10.0) is exploited in the wild; on-prem admins must upgrade to 2026.3 HF4.
N-able disclosed a third N-central vulnerability, CVE-2026-86218, a pre-authentication RCE rated CVSS 10.0, and released hotfix 2026.3 HF4 superseding build 2026.3.1.13. Huntress reproduced an exploit chain involving an authentication bypass (CVE-2026-86206/CVE-2026-86207) after a fully patched customer's N-central production server was compromised on September 4. Attackers appended strings like .invalid to account names and probed the /remoteControlAction.do?method=getPierDetails endpoint; Huntress worked with Cloudflare to disable adversary tunnel infrastructure. Hosted N-central instances are already patched; on-prem administrators must upgrade immediately.
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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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Attackers exploit critical SharePoint flaw after PoC goes public (CVE-2026-55040)
Attackers use Rapid7's public PoC to exploit CVE-2026-55040, a critical SharePoint authentication bypass patched in July 2026.
Rapid7 researcher Stephen Fewer published technical analysis and PoC exploit code for CVE-2026-55040, an authentication bypass in SharePoint caused by flaws in the JWT token validation pipeline. Threat intelligence firm Defused observed attackers using the PoC against SharePoint honeypots, though Microsoft has not yet confirmed in-the-wild exploitation. Chained with CVE-2026-63520, the flaw can yield unauthenticated remote code execution, per NHS England Digital. CISA is urging administrators to harden SharePoint deployments by limiting direct internet exposure and using Layer 7 reverse proxies.
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Network Security Trends: August
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