# Critical ShowDoc RCE Vulnerability Under Active Exploitation—Patch Now


## The Threat


A critical remote code execution vulnerability in ShowDoc, a widely-used document management and collaboration platform particularly popular among Chinese enterprises, is actively being exploited by threat actors against unpatched servers. Tracked as CVE-2025-0520 (also identified as CNVD-2020-26585), this flaw stems from improper file upload validation that allows unauthenticated attackers to upload and execute arbitrary code on vulnerable systems.


The vulnerability enables attackers to bypass file type restrictions and upload malicious files—typically PHP, JSP, or other executable scripts—that the server then executes with application-level privileges. Once an attacker achieves code execution, they gain full control over the ShowDoc instance and can pivot to broader network access, exfiltrate sensitive documents, or establish persistent backdoors for long-term compromise.


What makes this threat particularly urgent is the combination of high severity, active exploitation in the wild, and the likelihood that many ShowDoc deployments remain unpatched. Organizations using ShowDoc for internal document sharing and collaboration may not realize they're running vulnerable versions, making them prime targets for automated scanning and exploitation campaigns.


## Severity and Impact


| Attribute | Details |

|---|---|

| CVE ID | CVE-2025-0520 (CNVD-2020-26585) |

| CVSS v3.1 Score | 9.4 (Critical) |

| CVSS Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |

| CWE | CWE-434 (Unrestricted Upload of File with Dangerous Type) |

| Attack Vector | Network |

| Attack Complexity | Low |

| Privileges Required | None |

| User Interaction | None |

| Scope | Unchanged |

| Confidentiality Impact | High |

| Integrity Impact | High |

| Availability Impact | High |

| Exploitation Status | Active in the wild |


The CVSS score of 9.4 reflects the severity of unauthenticated remote code execution with no required privileges or user interaction. An attacker can exploit this vulnerability with a simple HTTP request, making it trivial to automate at scale.


## Affected Products


ShowDoc versions prior to the patched release are vulnerable. The following ShowDoc installations should be considered at immediate risk:


  • ShowDoc 2.x (all versions before patched build)
  • ShowDoc 3.x (versions through 3.x.x—consult official release notes for exact cutoff)

    • Organizations should check their current ShowDoc version in the admin panel or by reviewing deployment documentation. The vendor has released a patched version addressing this vulnerability; upgrading is the primary remediation path.


    ## Mitigations


    ### Immediate Actions


    1. Upgrade ShowDoc immediately to the latest patched version available from the official ShowDoc repository or vendor website. This is the most effective remediation.


    2. Identify affected instances by checking your ShowDoc version number. If running any version prior to the official patch release, assume compromise is possible.


    3. Assume compromise and investigate: Given active exploitation in the wild, organizations should review access logs for suspicious file uploads (especially executable file types: .php, .jsp, .asp, .exe, .sh) and examine web server logs for unusual activity during the period when the server was vulnerable.


    ### Interim Protections (if patching is delayed)


  • Restrict network access to ShowDoc instances using firewall rules, VPN requirements, or IP allowlisting. Limit ShowDoc exposure to trusted internal networks only.

  • Disable file upload functionality if possible through application settings until patching is complete, or restrict uploads to non-executable file types only (PDFs, Office documents, images).

  • Monitor upload directories for unexpected executable files. Set file system permissions to prevent web server execution in upload directories (e.g., chmod 644 and disable script execution via .htaccess or web server config).

  • Web Application Firewall (WAF) rules: Deploy rules to detect and block uploads of suspicious file extensions or MIME types mismatches.

  • Isolate ShowDoc from production systems if possible, restricting lateral movement potential in case of compromise.

    • ### Post-Incident Response


  • Once patched, review server logs, file systems, and database access logs for indicators of compromise.
  • Check for persistence mechanisms such as new admin accounts, backdoors, or webshells.
  • Rotate all credentials used within or connected to ShowDoc.
  • Restore from clean, verified backups if evidence of compromise is found.

    • ## References


  • Official ShowDoc Security Advisory: [ShowDoc official site](https://www.showdoc.cc/)
  • CVE-2025-0520 Details: Check MITRE CVE database and NIST NVD for full vulnerability details
  • CNVD-2020-26585: Chinese National Vulnerability Database entry
  • Patch Release: Consult ShowDoc GitHub repository or official vendor channels for the patched version and upgrade instructions

    • ---


    Recommendation: Organizations using ShowDoc should treat this vulnerability with the highest priority. The combination of critical severity, active exploitation, and ease of exploitation warrants immediate patching. Security teams should assume ShowDoc instances exposed to the internet or untrusted networks may already be compromised and conduct thorough forensic review alongside patching efforts.