Yonyou - CraftedSignal Threat Feedhttps://feed.craftedsignal.io/tags/yonyou/Trending threats, MITRE ATT&CK coverage, and detection metadata. Fed continuously.Hugoenhello@craftedsignal.iohello@craftedsignal.ioWed, 30 Sep 2026 22:37:11 +0000https://feed.craftedsignal.io/favicon-32x32.pngCraftedSignal Threat Feedhttps://feed.craftedsignal.io/3232https://feed.craftedsignal.io/favicon.svgArbitrary File Read in Yonyou U8 CRMhttps://feed.craftedsignal.io/briefs/2026-09-cve-2023-54403/Wed, 30 Sep 2026 22:37:11 +0000hello@craftedsignal.iohttps://feed.craftedsignal.io/briefs/2026-09-cve-2023-54403/An unauthenticated arbitrary file read vulnerability (CVE-2023-54403) in Yonyou U8 CRM allows attackers to bypass authentication and access sensitive files on the host server.Yonyou U8 CRM versions prior to V16.5 and V18 contain a critical arbitrary file read vulnerability located in the /ajax/getemaildata.php endpoint. The flaw exists due to insufficient validation of the filePath parameter, which allows an attacker to traverse directories and read arbitrary files from the underlying server filesystem. Furthermore, the endpoint includes an authentication bypass mechanism triggered by the DontCheckLogin=1 parameter, enabling unauthenticated remote attackers to successfully invoke the vulnerable function. Successful exploitation allows for the exfiltration of sensitive configuration files, including database credentials or service tokens, which can lead to full system compromise. The Shadowserver Foundation observed active exploitation of this vulnerability starting on October 14, 2023.

Impact

The vulnerability poses a high risk to organizations utilizing affected versions of Yonyou U8 CRM. If exploited, attackers can gain unauthorized access to sensitive system information, configuration files, and credentials stored on the server. This exposure facilitates further lateral movement within the network or complete takeover of the affected CRM instance.

Recommendation

Prioritize the upgrade of Yonyou U8 CRM to version V16.5, V18, or a later patched release. Deploy the detection rules provided below to identify attempts to interact with the vulnerable /ajax/getemaildata.php endpoint with the bypass parameter.

Rules

  • title: "Detects CVE-2023-54403 Exploitation - Attempted File Read in Yonyou U8 CRM" description: "Detects exploitation attempts targeting CVE-2023-54403 by identifying requests to /ajax/getemaildata.php containing the authentication bypass parameter." logsource: category: "webserver" detection: selection: cs-uri-stem: "/ajax/getemaildata.php" cs-uri-query|contains: "DontCheckLogin=1" cs-uri-query|contains: "filePath=" condition: selection level: "high" tags:
  • "attack.initial_access"
  • "attack.t1190" tests: positive:
  • name: "Exploitation request with bypass parameter" data:
  • cs-method: "GET" cs-uri-stem: "/ajax/getemaildata.php" cs-uri-query: "DontCheckLogin=1&filePath=../../etc/passwd" sc-status: "200" negative:
  • name: "Legitimate request without bypass parameter" data:
  • cs-method: "GET" cs-uri-stem: "/ajax/getemaildata.php" cs-uri-query: "filePath=email.eml" sc-status: "200" falsepositives:
  • "Legitimate administrative diagnostic tools if they utilize these parameters for maintenance." handoff: detection_confidence: "high" required_telemetry:
  • log_source: "Web server access logs" event_or_channel: "HTTP requests" required_fields:
  • "cs-uri-stem"
  • "cs-uri-query" availability: "available" notes: "Requires full logging of URI query parameters." validation: status: "needs_environment_validation" steps:
  • "Send a crafted GET request to the endpoint with the specified query string in a isolated lab environment." expected_telemetry: "Web server log entry matching the selection criteria." pass_criteria: "Log entry identified in the SIEM." known_evasions:
  • "URL encoding or obfuscation of the filePath parameter." limitations:
  • "Will not detect exploitation if parameters are sent via POST body instead of URI query, depending on web server logging configuration." tuning:
  • source: "None" guidance: "Review for internal testing activity before promoting to active blocking." portability_notes:
  • platform: "SIEM" note: "Ensure field names match your specific web server log schema (e.g., Splunk/ELK mappings)." suggested_owner: "Detection Engineering"
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