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CVE-2026-80235 – Unauthenticated Arbitrary File Upload / RCE – EFence ≤ 1.2.66 DB Ver:56

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Summary

CVE-2026-80235 is a critical arbitrary file upload vulnerability (CWE-434) affecting EFence, a product developed by Thinking Software Technology. The flaw allows unauthenticated remote attackers to upload and execute web shell backdoors on the underlying server, resulting in full remote code execution. The issue carries a CVSS v3.1 base score of 9.8 (Critical) and was publicly disclosed on August 26, 2026 via Taiwan’s TWCERT/CC advisory TVN-202608010.

Technical details

  • Root cause: EFence fails to properly restrict the type of files that can be uploaded through its file upload functionality, allowing dangerous file types (e.g., web shell scripts) to be stored and subsequently executed by the web server.
  • Trigger conditions: An attacker sends a crafted upload request to the vulnerable EFence file upload endpoint; no valid session, credentials, or user interaction are required.
  • Attack vector: Network-based (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N).
  • Impact: Successful exploitation allows an unauthenticated attacker to place and execute an arbitrary web shell, leading to complete compromise of confidentiality, integrity, and availability of the affected system.
  • Two related vulnerabilities were disclosed in the same advisory: CVE-2026-80236 (unauthenticated SQL injection via the upload functionality, CVSS 8.2) and CVE-2026-80237 (authenticated arbitrary file upload, CVSS 8.8). These are distinct CVEs and not covered by this post.
  • The vulnerability was reported by researchers Sideman and Linwz of DEVCORE.

Affected software

  • EFence, versions 1.2.66 DB Ver:56 and earlier (all prior versions are considered affected).

Severity

  • CVSS v3.1 Base Score: 9.8 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade EFence to version 1.2.67 DB Ver:57 or later, which addresses this vulnerability.
  • If patching is not immediately possible: Restrict network access to the EFence file upload endpoint to trusted management networks only, disable or block the vulnerable upload functionality at the web server/reverse proxy layer, and monitor uploaded file directories for unexpected executable or script files (e.g., web shells).
  • Review server logs and uploaded file directories for indicators of compromise predating the patch deployment, given the vulnerability requires no authentication.

References

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