CVE Details

CVE-2026-55040 Microsoft SharePoint Weak Authentication Vulnerability
Published: 2026-08-18 CVSS: 9.1 CRITICAL Product: Microsoft SharePoint Due Date: 2026-08-21

Microsoft SharePoint contains a weak authentication vulnerability which allows an unauthorized attacker to bypass a security feature over a network.

GitHub PoC

Warning: GitHub PoC repositories are unverified. Some may be fake or contain malware. Use caution and review code before running anything.
  • killvxk/gitweekly • ⭐ 108 • 2025-07-22 • Conf: 95.0%
  • 收集各种有趣的github项目
  • webpro255/awesome-ai-agent-attacks • ⭐ 65 • 2026-04-07 • Conf: 95.0%
  • A curated timeline of real AI agent security incidents, breaches, and vulnerabilities (2024-2026). Every entry sourced and dated.
  • sfewer-r7/CVE-2026-55040 • ⭐ 53 • 2026-08-06 • Conf: 95.0%
  • Microsoft SharePoint JWT Authentication Bypass (CVE-2026-55040)
  • l0ggg/CVE-2026-55040 • ⭐ 2 • 2026-07-28 • Conf: 95.0%
  • Exploit code for CVE-2026-55040, it can create auth header for any validate account.

FIRST EPSS

EPSS estimates the probability of exploitation in the next 30 days. Higher values indicate higher likelihood of real-world exploitation.

Timeline

CVE Stalker KEV MITRE GitHub FIRST (EPSS)

MITRE

CVSS

  • Score: 9.1
  • Severity: CRITICAL
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C

SSVC

  • Exploitation: poc
  • Automatable: yes
  • Technical Impact: total

References

Show Raw Data
Key Remaining Key Value
dataType CVE_RECORD
dataVersion 5.2
cveMetadata > cveId CVE-2026-55040
cveMetadata > assignerOrgId f38d906d-7342-40ea-92c1-6c4a2c6478c8
cveMetadata > state PUBLISHED
cveMetadata > assignerShortName microsoft
cveMetadata > dateReserved 2026-06-16T14:13:49.835Z
cveMetadata > datePublished 2026-07-14T17:09:00.641Z
cveMetadata > dateUpdated 2026-08-18T17:16:59.160Z
containers > cna > title Microsoft SharePoint Server Security Feature Bypass Vulnerability
containers > cna > datePublic 2026-07-14T14:00:00.000Z
containers > cna > cpeApplicability > 0 > nodes > 0 > operator OR
containers > cna > cpeApplicability > 0 > nodes > 0 > negate False
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 0 > vulnerable True
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 0 > criteria cpe:2.3:a:microsoft:sharepoint_server_2016:*:*:*:*:enterprise:*:*:*
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 0 > versionStartIncluding 16.0.0
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 0 > versionEndExcluding 16.0.5561.1001
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 1 > vulnerable True
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 1 > criteria cpe:2.3:a:microsoft:sharepoint_server_2019:*:*:*:*:*:*:*:*
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 1 > versionStartIncluding 16.0.0
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 1 > versionEndExcluding 16.0.10417.20175
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 2 > vulnerable True
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 2 > criteria cpe:2.3:a:microsoft:sharepoint_server:*:*:*:*:subscription:*:*:*
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 2 > versionStartIncluding 16.0.0
containers > cna > cpeApplicability > 0 > nodes > 0 > cpeMatch > 2 > versionEndExcluding 16.0.19725.20434
containers > cna > affected > 0 > vendor Microsoft
containers > cna > affected > 0 > product Microsoft SharePoint Enterprise Server 2016
containers > cna > affected > 0 > platforms > 0 x64-based Systems
containers > cna > affected > 0 > versions > 0 > version 16.0.0
containers > cna > affected > 0 > versions > 0 > lessThan 16.0.5561.1001
containers > cna > affected > 0 > versions > 0 > versionType custom
containers > cna > affected > 0 > versions > 0 > status affected
containers > cna > affected > 1 > vendor Microsoft
containers > cna > affected > 1 > product Microsoft SharePoint Server 2019
containers > cna > affected > 1 > platforms > 0 x64-based Systems
containers > cna > affected > 1 > versions > 0 > version 16.0.0
containers > cna > affected > 1 > versions > 0 > lessThan 16.0.10417.20175
containers > cna > affected > 1 > versions > 0 > versionType custom
containers > cna > affected > 1 > versions > 0 > status affected
containers > cna > affected > 2 > vendor Microsoft
containers > cna > affected > 2 > product Microsoft SharePoint Server Subscription Edition
containers > cna > affected > 2 > platforms > 0 x64-based Systems
containers > cna > affected > 2 > versions > 0 > version 16.0.0
containers > cna > affected > 2 > versions > 0 > lessThan 16.0.19725.20434
containers > cna > affected > 2 > versions > 0 > versionType custom
containers > cna > affected > 2 > versions > 0 > status affected
containers > cna > descriptions > 0 > value Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
containers > cna > descriptions > 0 > lang en-US
containers > cna > problemTypes > 0 > descriptions > 0 > description CWE-1390: Weak Authentication
containers > cna > problemTypes > 0 > descriptions > 0 > lang en-US
containers > cna > problemTypes > 0 > descriptions > 0 > type CWE
containers > cna > problemTypes > 0 > descriptions > 0 > cweId CWE-1390
containers > cna > providerMetadata > orgId f38d906d-7342-40ea-92c1-6c4a2c6478c8
containers > cna > providerMetadata > shortName microsoft
containers > cna > providerMetadata > dateUpdated 2026-08-18T17:16:59.160Z
containers > cna > references > 0 > name Microsoft SharePoint Server Security Feature Bypass Vulnerability
containers > cna > references > 0 > tags > 0 vendor-advisory
containers > cna > references > 0 > tags > 1 patch
containers > cna > references > 0 > url https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040
containers > cna > metrics > 0 > format CVSS
containers > cna > metrics > 0 > scenarios > 0 > lang en-US
containers > cna > metrics > 0 > scenarios > 0 > value GENERAL
containers > cna > metrics > 0 > cvssV3_1 > version 3.1
containers > cna > metrics > 0 > cvssV3_1 > baseSeverity CRITICAL
containers > cna > metrics > 0 > cvssV3_1 > baseScore 9.1
containers > cna > metrics > 0 > cvssV3_1 > vectorString CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C
containers > adp > 0 > references > 0 > url https://www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/
containers > adp > 0 > references > 0 > tags > 0 technical-description
containers > adp > 0 > references > 1 > url https://github.com/sfewer-r7/CVE-2026-55040
containers > adp > 0 > references > 1 > tags > 0 exploit
containers > adp > 0 > metrics > 0 > other > type ssvc
containers > adp > 0 > metrics > 0 > other > content > timestamp 2026-08-13T03:55:25.706009Z
containers > adp > 0 > metrics > 0 > other > content > id CVE-2026-55040
containers > adp > 0 > metrics > 0 > other > content > options > 0 > Exploitation poc
containers > adp > 0 > metrics > 0 > other > content > options > 1 > Automatable yes
containers > adp > 0 > metrics > 0 > other > content > options > 2 > Technical Impact total
containers > adp > 0 > metrics > 0 > other > content > role CISA Coordinator
containers > adp > 0 > metrics > 0 > other > content > version 2.0.3
containers > adp > 0 > title CISA ADP Vulnrichment
containers > adp > 0 > providerMetadata > orgId 134c704f-9b21-4f2e-91b3-4a467353bcc0
containers > adp > 0 > providerMetadata > shortName CISA-ADP
containers > adp > 0 > providerMetadata > dateUpdated 2026-08-13T13:16:05.985Z