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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SharePoint CVE-2026-55040 Comes Under Attack Following Public Exploit
Attackers are actively exploiting critical SharePoint authentication bypass CVE-2026-55040 (CVSS 9.1) days after Rapid7 released a public PoC.
CVE-2026-55040 is a critical authentication bypass (CVSS 9.1) in SharePoint Server Subscription Edition that lets unauthenticated attackers forge JWT tokens and impersonate any user, including administrators. Microsoft patched it in July 2026 Patch Tuesday, but Rapid7 published a technical write-up and Python PoC on GitHub on August 12, and Defused quickly observed attackers running the PoC against SharePoint honeypots. KEVIntel recorded 12 exploitation attempts since July 19, with eight occurring on August 12-13 from IP addresses in Hong Kong, Japan, the Netherlands, Taiwan and the U.S. Admin-level SharePoint access exposes documents and data modification and can serve as a foothold into broader Microsoft 365 infrastructure; unpatched instances should apply the July update immediately.
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Public PoC triggers active exploitation of critical SharePoint RCE vulnerability CVE-2026
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ToolShell Exploit: Critical SharePoint Zero
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Hackers Exploit SharePoint Zero-Day Since July 7 to Steal Keys, Maintain Persistent Access
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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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2026-009: Critical Vulnerabilities in Microsoft SharePoint
WatchTowr observed active exploitation of SharePoint RCE CVE-2026-50522 (CVSS 9.8), part of an ongoing wave of exploited on-prem SharePoint flaws patched by Microsoft.
On 14 July 2026 Microsoft released updates for critical SharePoint Server RCE flaws, including CVE-2026-50522 (CVSS 9.8), a deserialisation vulnerability possibly exploitable without authentication. On 20 July 2026 WatchTowr published PoC exploit code and observed active exploitation of CVE-2026-50522, prompting CISA to urge SharePoint hardening. The advisory also covers recently fixed SharePoint flaws: CVE-2026-32201 (6.5, spoofing), CVE-2026-45659 (8.8, authenticated RCE), CVE-2026-56164 (9.8, unauthenticated privilege escalation), and CVE-2026-58644 (9.8, unauthenticated RCE). Affected products include SharePoint Server Subscription Edition, 2019, and Enterprise Server 2016; CERT-EU recommends immediate patching, credential rotation, and compromise assessments.
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ToolShell: Details of CVEs affecting SharePoint servers
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2026-004: Critical Vulnerability in SharePoint Exploited
CVE-2026-20963 (CVSS 9.8), an unauthenticated RCE in on-prem SharePoint, was added to CISA's KEV on 18 March 2026 and is actively exploited.
CERT-EU warns about CVE-2026-20963, a CVSS 9.8 unauthenticated remote code execution flaw in SharePoint caused by deserialisation of untrusted data, affecting SharePoint Server Subscription Edition, 2019, and Enterprise Server 2016. Microsoft raised the CVSS score on 17 March 2026 and the flaw entered CISA's Known Exploited Vulnerabilities catalogue on 18 March 2026. Three additional SharePoint RCE flaws (CVE-2026-26106, CVE-2026-26113, CVE-2026-26114) were fixed in the March 2026 release. CERT-EU urges immediate patching of internet-facing servers plus AMSI Full Mode, EDR deployment, ASP.NET machine key rotation, and compromise assessments.
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U.S. CISA adds Apple macOS, Microsoft SharePoint, Broadcom VMware vCenter, and Microsoft IKE flaws to its Known Exploited Vulnerabilities catalog
CISA adds actively exploited flaws in Microsoft IKE, SharePoint, VMware vCenter, and macOS Screen Sharing to KEV catalog, due August 21.
CISA added four vulnerabilities to its Known Exploited Vulnerabilities catalog: CVE-2026-33824 (Windows IKE remote code execution, CVSS 9.8), CVE-2026-55040 (SharePoint JWT authentication bypass, CVSS 9.1), CVE-2026-59310 (VMware vCenter Syslog path traversal, CVSS 9.8), and CVE-2026-65400 (macOS Screen Sharing improper authentication). The SharePoint flaw combines four weaknesses including alg:none JWT forging to impersonate any user, with Defused researchers observing attackers using Rapid7's PoC against honeypots. The Dutch NCSC confirmed active exploitation of the macOS Screen Sharing flaw on August 15, 2026. Federal agencies must patch by August 21, 2026.
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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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CISA Adds Exploited SharePoint RCE Zero-Day CVE-2026
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CISA Orders Urgent Patching After Chinese Hackers Exploit SharePoint Flaws in Live Attacks
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Attackers Exploit SharePoint Authentication Bypass After Public PoC Release
Attackers exploit SharePoint authentication bypass CVE-2026-55040 (CVSS 9.1) after Rapid7's PoC release, with 12 exploitation attempts recorded since July 19, 2026.
Microsoft patched CVE-2026-55040 in its July 2026 Patch Tuesday; the 9.1-severity flaw chains four weaknesses in SharePoint's JWT token validation pipeline, letting unauthenticated attackers forge valid JWTs and impersonate any SharePoint site user or administrator. Threat actors began exploiting the bug after Rapid7 released a Python PoC that forges tokens and enumerates domain users by SID. KEVIntel telemetry shows 12 exploitation attempts since July 19, 2026, eight of them on August 12-13 following the PoC release, originating from eight IPs across Hong Kong, Japan, the Netherlands, Taiwan, and the U.S. This is the fifth SharePoint vulnerability exploited this year, alongside CVE-2026-45659, CVE-2026-56164, CVE-2026-58644, and CVE-2026-50522.
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SharePoint RCE CVE-2026-45659 Added to CISA KEV After Active Exploitation
CISA adds actively exploited SharePoint RCE CVE-2026-45659 (CVSS 8.8) to KEV; an August 11 update confirms ransomware groups are exploiting the flaw.
CVE-2026-45659 is a deserialization of untrusted data RCE in Microsoft SharePoint Server affecting Subscription Edition, 2019, and 2016, patched by Microsoft in May 2026. An authenticated attacker with at least Site Member permissions can execute code remotely over the network. CISA added the flaw to its KEV catalog on July 2 with a July 4 deadline for federal agencies, and on August 11 confirmed ransomware groups are exploiting it. Microsoft separately described Storm-2603 (Warlock ransomware) and an unrelated actor co-existing in one network, with initial access likely via the Gladinet Triofox flaw CVE-2025-11371 (CVSS 9.1).
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Researcher Drops New Windows Zero-Day PoC Hours After Microsoft Patch Tuesday
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Critical macOS, SharePoint, vCenter, and Microsoft IKE Flaws Under Active Exploitation
CISA added four critical actively exploited flaws to KEV: macOS Screen Sharing, SharePoint, VMware vCenter, and Microsoft IKE, with APT and ransomware use.
CISA added CVE-2026-65400 (macOS Screen Sharing, CVSS 9.8), CVE-2026-55040 (SharePoint, CVSS 9.1), CVE-2026-59310 (VMware vCenter, CVSS 9.8) and CVE-2026-33824 (Microsoft IKE Service Extensions, CVSS 9.8) to the KEV catalog. The macOS flaw was abused to deliver a Monero miner, while the vCenter bug was exploited by a suspected China-nexus APT to install reverse_ssh backdoors and Babuk-derived ransomware across 361 victim IPs in 47 countries. Unit 42 linked CVE-2026-33824 to a Chinese-speaking actor running an AI-enabled campaign using DeepSeek. FCEB agencies must patch by August 21, 2026 under BOD 26-04.
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CISA adds Microsoft SharePoint bug disclosed at Pwn2Own to its Known Exploited Vulnerabilities catalog
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Critical SharePoint RCE CVE-2026-50522 Under Active Exploitation After ...
watchTowr reports active exploitation of SharePoint CVE-2026-50522 after a public PoC, with attackers stealing machine keys for persistence.
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