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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

Rapid7 Analysis: Microsoft SharePoint Remote Code Execution (CVE-2026-63520)

Rapid7 published technical analysis of CVE-2026-63520, a remote code execution vulnerability in Microsoft SharePoint.

Rapid7 released an analysis covering CVE-2026-63520, a remote code execution flaw affecting Microsoft SharePoint. SharePoint is widely deployed in enterprise environments, making exposed, unpatched servers a likely target for exploitation. Defenders should consult the Rapid7 write-up for exposure checks and patch guidance. The available text does not confirm active exploitation at this time.

Rapid7 Blog · 23d agoVulnerabilityCVE-2026-635201

North Korean Hackers Deploy New Linux Espionage Toolkit

Rapid7 says North Korea-aligned actors use a new Linux espionage toolkit (ted HAProxy backdoor, CurlRAT) against South Korean automotive and media targets.

Rapid7 reports a stealthy Linux framework comprising a custom HAProxy backdoor ('ted'), trojanized system binaries (agetty, atd, crond, polkitd, sshd), an SSH keylogger, and CurlRAT that polls C&C every 12 hours. Initial access came via a Groupware login portal flaw, with credential harvesting enabling lateral movement to internal systems. The toolkit supports long-term surveillance, HTTP traffic interception/injection, and drive-by downloads, likely in use since late 2024. Infrastructure and artifacts overlap Operation SyncHole, suggesting Lazarus or APT37 involvement.

SecurityWeek · 9d agoThreat actor in the wild1

DPRK APTs: Ted backdoor and curlRAT target South Korean media and automotive sectors

Rapid7 uncovered a DPRK-linked Linux toolkit using a HAProxy-embedded ted backdoor, SSH keylogger, and curlRAT against South Korean media and automotive firms.

Rapid7 Labs identified a previously undocumented framework attributed with medium confidence to DPRK actors, targeting South Korean automotive and media organizations likely since early 2025. The toolkit embeds a backdoor compiled into HAProxy 2.8.12 using its filter API, plus trojanized crond, agetty, atd, sshd, and polkitd, an SSH keylogger storing credentials under /var/lib/sshd/, and a curl-based RAT with a watchdog thread. It enables remote command execution, malicious script injection into served webpages (a watering-hole loop), credential harvesting, and long-term surveillance. Hardcoded C2s are associated with APT37 via ThreatFox, and exposed groupware portals and mail servers align with Kimsuky tradecraft; the initial access vector and any CVE remain unconfirmed.

Rapid7 Blog · 12d agoThreat actor in the wild1

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

8,539 Reasons To Rethink How Vulnerabilities Get Patched

Rapid7 counted 8,539 high and critical CVEs in Q2 2026, double last year, with PoC availability up 76%.

Rapid7's Q2 2026 Threat Landscape Report tallied 8,539 high- and critical-severity vulnerability disclosures, twice the number recorded in Q2 2025, with newly disclosed flaws having public proof-of-concept code up 76% year over year. Of newly exploited vulnerabilities, 62% were network-exploitable and required neither authentication nor user interaction. Fake CAPTCHA and ClickFix social engineering accounted for 31.8% of incident response cases, the United States recorded 881 listed ransomware victims, and APT28 exploited SOHO routers for DNS hijacking while Iranian groups targeted US industrial control and OT systems.

Help Net Security · 28d agoResearch

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