PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-77900 Microsoft CVE debrief

The Azure App Service Remote Code Execution Vulnerability (CVE-2026-77900) is a critical vulnerability that allows unauthorized code execution over a network due to missing authentication for a critical function in Azure App Service for Linux. This vulnerability has a CVSS score of 9.8, indicating a high severity. The vulnerability was published on 2026-10-08T22:15:30.299Z and last modified on 2026-10-10T03:55:23.226Z. Defenders should prioritize verifying exposure of Azure App Service for Linux deployments and applying vendor-provided patches to prevent exploitation. The CVE record and NVD entry provide details on the vulnerability, but vendor-provided patch details and affected  

Vendor
Microsoft
Product
Azure App Service for Linux
CVSS
CRITICAL 9.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-10-08
Original CVE updated
2026-10-10
Advisory published
2026-10-08
Advisory updated
2026-10-10

Who should care

Defenders responsible for Azure App Service for Linux deployments should assess exposure and prioritize patching to prevent unauthorized code execution.

Why it matters

CVE-2026-77900 is a critical vulnerability in Azure App Service for Linux that allows unauthorized code execution over a network. Defenders should prioritize verifying exposure and applying patches to prevent exploitation.

  • Verify exposure of Azure App Service for Linux deployments to unauthorized code execution
  • Apply patches to prevent exploitation
  • Monitor for signs of unauthorized code execution attempts

Technical summary

The Azure App Service Remote Code Execution Vulnerability (CVE-2026-77900) is a critical vulnerability with a CVSS score of 9.8. It allows an unauthorized attacker to execute code over a network due to missing authentication for a critical function in Azure App Service for Linux. The vulnerability was published on 2026-10-08T22:15:30.299Z and last modified on 2026-10-10T03:55:23.226Z.

Defensive priority

Defenders should prioritize verifying exposure of Azure App Service for Linux deployments and applying vendor-provided patches.

Recommended defensive actions

  • Verify exposure of Azure App Service for Linux deployments
  • Apply vendor-provided patches
  • Monitor for unauthorized code execution attempts

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, but vendor-provided patch details and affected version specifics require verification.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-77900 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-77900

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-77900 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-77900

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Azure App Service Remote Code Execution Vulnerability

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/77xxx/CVE-2026-77900.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-77900

    Supplemental source - vendor-advisory, patch

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.