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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.

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

Artifactory Under Attack: In-the-Wild Exploitation of CVE-2026-42016, CVE-2026-42018 & CVE-2026-82329

Wiz Research confirms in-the-wild exploitation of three JFrog Artifactory vulnerabilities, chained to gain administrative control, deploy Groovy plugins, and install Rust backdoors.

Wiz Research identified active exploitation of CVE-2026-42016, CVE-2026-42018, and CVE-2026-82329 in JFrog Artifactory between August 15 and September 8, 2026. Attackers chain the anonymous-token exposure (CVE-2026-42018) with the token scope-validation flaw (CVE-2026-42016) to obtain admin-scoped tokens, while CVE-2026-82329 allows unauthenticated administrative access in default configurations. Observed post-exploitation includes persistent administrator accounts created in under five minutes, malicious Groovy plugin deployment, ad-hoc command execution, Rust-based C2 backdoors dropped to writable paths, and webshell uploads. Wiz measured that 59-62% of organizations running Artifactory remained vulnerable to the chained CVEs weeks after disclosure, and the vulnerabilities were already included in CISA KEV.

Wiz Blogupdated · 1d agofirst · 5d agoExploit / PoC in the wild 7 sourcesCVE-2026-42016CVE-2026-42018CVE-2026-823292· 1 read

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