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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.

Security Affairs · Aug 13, 2026Exploit / PoC in the wildCVE-2026-55040

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.

Help Net Security · Aug 13, 2026Exploit / PoC in the wildCVE-2026-55040CVE-2026-63520

Rapid7 Analysis: Microsoft SharePoint JWT Token Authentication Bypass (CVE-2026-55040)

Rapid7's analysis of SharePoint auth bypass CVE-2026-55040 includes a PoC for unauthenticated admin-level operations.

Rapid7 and Microsoft disclosed CVE-2026-55040, an authentication bypass in Microsoft SharePoint, on July 14, 2026. The flaw stems from multiple issues in SharePoint's JWT token validation pipeline, allowing a remote unauthenticated attacker to bypass authentication and perform operations as a site user or administrator. Rapid7 has now published a technical analysis and a proof-of-concept script, based on SharePoint Server Subscription Edition.

Rapid7 Blog · Aug 11, 2026VulnerabilityCVE-2026-550401

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.

The Hacker News · Aug 15, 2026Exploit / PoC in the wildCVE-2026-55040CVE-2026-45659CVE-2026-56164+2 CVEs

September 2026 Patch Tuesday forecast: All we need is more time

September 2026 Patch Tuesday forecast expects record CVE volume after August's 398 fixes, with SharePoint flaws CVE-2026-55040 and CVE-2026-63520 actively exploited.

This Patch Tuesday forecast column notes August 2026 Patch Tuesday was the second largest ever with 398 resolved CVEs, yet only one was confirmed actively exploited. SharePoint flaws CVE-2026-55040 and CVE-2026-63520 are being chained for authentication bypass and remote code execution in active attacks against unpatched servers. Microsoft Defender's ShieldBreak elevation of privilege flaw (CVE-2026-69414) is publicly disclosed with PoC code and a fix is expected, while Chrome CVE-2026-85046 was reported exploited in the wild. Several products, including Windows 11 24H2 Home/Pro and Exchange Server 2016/2019 ESU, reach end of support in October 2026.

Help Net Security · 6d agoAdvisory in the wildCVE-2026-55040CVE-2026-63520CVE-2026-62911+5 CVEs1

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.

Security Affairs · 27d agoExploit / PoC in the wildCVE-2026-33824CVE-2026-55040CVE-2026-59310+1 CVEs

Microsoft Patches 398 Flaws Including a Windows Driver Zero

Microsoft's August Patch Tuesday fixes 398 CVEs, including actively exploited Windows zero-day CVE-2026-68820 used by Lazarus for SYSTEM privilege escalation.

Microsoft's August 2026 Patch Tuesday release addresses 398 new vulnerabilities, 62 rated Critical by the Zero Day Initiative, with CVE-2026-68820 (CVSS 7.0), a use-after-free in the afd.sys Windows kernel driver, the only flaw flagged as actively exploited. Check Point Research attributed exploitation of the privilege escalation bug to Lazarus' Operation Dream Job campaign. Four unauthenticated remote code execution flaws rated 9.8 affect Windows DNS Server (CVE-2026-62878, called wormable by ZDI), Windows Deployment Services (CVE-2026-62893), Microsoft QUIC (CVE-2026-62815) and HPC Pack (CVE-2026-59124). The release also completes a two-part SharePoint fix with RCE component CVE-2026-63520, following July's authentication bypass fix CVE-2026-55040.

The Hacker News · Aug 11, 2026Exploit / PoC in the wildCVE-2026-68820CVE-2026-62878CVE-2026-62893+4 CVEs

Researchers Disclose AI-Assisted SharePoint Exploit Chain Reaching Unauthenticated RCE

Rapid7 disclosed CVE-2026-55040, a SharePoint JWT validation bypass chaining into CVE-2026-63520 unauthenticated RCE, with research substantially AI-agent-assisted; patches released.

Rapid7 disclosed CVE-2026-55040 (CVSS 9.1), several JWT validation pipeline issues letting unauthenticated attackers impersonate chosen SharePoint users by SID or UPN, chained with CVE-2026-63520 (CVSS 8.1), an unsafe .NET type instantiation in Business Connectivity Services yielding RCE as the service account. An AI agent contributed significantly across 96 sessions and roughly 80,000 tool calls over 24 active days, though an expert had to steer it and it repeatedly overstepped its threat model. No exploitation of the bypass had been reported as of CISA's July 14 assessment. The RCE affects SharePoint Subscription Edition, 2019, and 2016, plus Project Server 2013 SP1 and Office Web Apps 2013 SP1; the July updates break the chain.

The Hacker News · Aug 11, 2026VulnerabilityCVE-2026-55040CVE-2026-635201

CVE-2026-63520: Microsoft SharePoint Remote Code Execution (FIXED)

Rapid7 and Microsoft disclose CVE-2026-63520, a SharePoint RCE that chains with CVE-2026-55040 for unauthenticated RCE; patches released.

Rapid7 Labs' zero-day research project on Microsoft SharePoint uncovered two vulnerabilities that, when chained, achieve unauthenticated remote code execution. The second flaw in the chain, CVE-2026-63520, affects all supported versions of Microsoft SharePoint and has been disclosed and fixed. The first chain component, CVE-2026-55040, was disclosed by Rapid7 and Microsoft the previous month.

Rapid7 Blog · Aug 11, 2026VulnerabilityCVE-2026-63520CVE-2026-550401

Week in review: Salesforce and ServiceNow portals exposed for 17 months, exploited Metabase 0-day

Weekly digest: exploited Metabase zero-day breached Framework; Salesforce/ServiceNow portals read for 17 months; Microsoft patched 400+ flaws.

Help Net Security's week in review aggregates top stories: a 'City-Forum' campaign tracked by Reco has been pulling records from Salesforce and ServiceNow portals worldwide for 17 months, and Framework suffered a breach via an exploited Metabase zero-day exposing customer contact and IP data. It also covers Microsoft's August 2026 Patch Tuesday fixing 400+ flaws including exploited zero-day CVE-2026-68820, Cisco's fix for exploited firewall DoS bug CVE-2026-20349 (added to CISA KEV), and a second N-able N-central hotfix for actively exploited CVE-2026-18577. Other items include GitHub expanding Dependabot malware alerts to eight package ecosystems and EU AI Act enforcement beginning on 2 August 2026.

Help Net Security · Aug 16, 2026Industry in the wildCVE-2026-18577CVE-2026-68820CVE-2026-203491

CVE-2026-33824: CISA Flags Windows IKE RCE as Exploited

CISA added four actively exploited vulnerabilities to its KEV catalog, headlined by CVE-2026-33824, a Windows IKE Service Extensions remote code execution flaw.

CISA's KEV addition, dated August 18, covers CVE-2026-33824 in Windows IKE Service Extensions, CVE-2026-55040 in on-premises Microsoft SharePoint Server, CVE-2026-59310 in Broadcom VMware vCenter, and CVE-2026-65400 in Apple macOS Screen Sharing. KEV listing confirms observed exploitation in the wild. Three of the four products are frequently deployed as high-value enterprise infrastructure, including remote-access endpoints and collaboration platforms.

Web discovery (articles for new exploits & KEV entries) · 7d agoExploit / PoC in the wildCVE-2026-33824CVE-2026-55040CVE-2026-59310+1 CVEs

August 2026 CVE Landscape

Insikt Group catalogs 73 high-impact August 2026 CVEs (43 Very Critical), including PaperCut, Zimbra, and Metabase flaws actively exploited or weaponized.

Recorded Future's Insikt Group identified 73 high-impact vulnerabilities in August 2026, 43 rated Very Critical, spanning 45 vendors with Microsoft accounting for roughly 11%. 31 vulnerabilities surfaced via CISA's KEV catalog, with others validated via open sources, vendor telemetry, and honeypot data. New Nuclei detection templates were released for CVE-2025-62593 (Ray), CVE-2026-72898 (Metabase), and CVE-2026-9198 (IBM Langflow). The report also highlights two AI-assisted operations: UAT-10147 exploited Zimbra, AjaxPro, Nacos, and Telerik servers before using DeepAudit and PentestGPT post-compromise, while a separate Chinese-speaking actor weaponized Hermes Agent and DeepSeek in a failed attempt.

Recorded Future · 7d agoVulnerability in the wildCVE-2025-62593CVE-2026-72898CVE-2026-9198+4 CVEs

Risky Bulletin: Russia starts blocking DoH and DoT

Russian users report blocks on DoH and DoT servers, including Cloudflare 1.1.1.1 and Google 8.8.8.8, in an apparent censorship crackdown.

Russian internet users began reporting failures connecting to DNS-over-HTTPS and DNS-over-TLS servers, suggesting a government crackdown on the two privacy protocols. The blocks reportedly cover Cloudflare's 1.1.1.1 and Google's 8.8.8.8 resolvers; Roskomnadzor has not officially confirmed the action. The agency tested a similar block in March on Beeline's network and had named DoH for blocking as early as 2021. The bulletin also briefly notes state-sponsored phishing of EU officials, a DDoS against Norway's Digdir, the ReliaQuest/ShinyHunters dispute, and older ransomware and breach disclosures.

Risky Business News · 20d agoPolicy & legal1

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.

The Hacker News · 27d agoExploit / PoC in the wildCVE-2026-65400CVE-2026-55040CVE-2026-59310+1 CVEs

Microsoft patches 400+ vulnerabilities, one zero-day under attack (CVE-2026-68820)

Microsoft's August 2026 Patch Tuesday fixes 400+ vulnerabilities, including an actively exploited Windows zero-day (CVE-2026-68820) used by North Korean attackers.

Microsoft's August 2026 Patch Tuesday fixes over 400 vulnerabilities, including CVE-2026-68820, a use-after-free in the Windows Ancillary Function Driver exploited in the wild by North Korean actors deploying a kernel-mode rootkit in Operation Dream Job. Critical unauthenticated remote code execution flaws in Microsoft QUIC (CVE-2026-62815) and Windows DNS (CVE-2026-62878) were also patched, alongside a SharePoint RCE chain combining CVE-2026-63520 with CVE-2026-55040. Researcher Nightmare-Eclipse released ShieldBreak, a PoC bypassing the July RoguePlanet Microsoft Defender patch (CVE-2026-50656), confirmed working by Will Dormann on Windows 11.

Help Net Security · Aug 12, 2026Exploit / PoC in the wildCVE-2026-68820CVE-2026-62832CVE-2026-72971+6 CVEs