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CVE-2026-9181 – Unauthenticated Directory Traversal / Sensitive File Read – Esri ArcGIS Server 12…

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Summary

CVE-2026-9181 is a critical directory traversal vulnerability in Esri ArcGIS Server affecting all versions 12.0 and prior. An unauthenticated, remote attacker can exploit this flaw by sending crafted path parameters over the network to read sensitive files from the underlying system. With a CVSS v3.1 base score of 9.8 (Critical), this vulnerability requires no privileges and no user interaction, making it immediately actionable for any attacker able to reach an exposed ArcGIS Server instance.

Technical details

  • Root cause: Improper limitation of a pathname to a restricted directory (CWE-22 — Path Traversal); the server fails to adequately sanitize or restrict path parameters submitted by the client, allowing directory traversal sequences to escape the intended file-system boundary.
  • Trigger conditions: Sending a specially crafted HTTP request containing path traversal sequences to a reachable ArcGIS Server endpoint. No authentication token, account credential, or prior foothold is required.
  • Attack vector: Network-accessible, low attack complexity, no privileges required, no user interaction (CVSS vector: AV:N/AC:L/PR:N/UI:N).
  • Impact: Successful exploitation allows an unauthenticated attacker to read arbitrary sensitive files from the server’s filesystem — including configuration files, credentials, and other restricted data — potentially enabling further system compromise or lateral movement within the enterprise environment.

Affected software

  • Esri ArcGIS Server 12.0 and all prior releases
  • Confirmed affected version branches: 12.0, 11.5, 11.4, 11.3, 11.1

Severity

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

Mitigation and recommended actions

  • Immediate — Apply the vendor patch: Esri released the ArcGIS Server Security 2026 Update 1 Patch on May 27, 2026, addressing this vulnerability. An ArcGIS Server Security 2026 Update 2 Patch has also been subsequently released. Esri strongly recommends all ArcGIS Enterprise customers running versions 12.0, 11.5, 11.4, 11.3, or 11.1 apply the latest available security patch without delay.
  • Interim mitigation (if patching is not immediately possible): Esri explicitly acknowledges this vulnerability can be mitigated by deploying a Web Application Firewall (WAF) using the recommended rulesets referenced in the Esri Enterprise Hardening Guide. Additionally, restrict public internet exposure of ArcGIS Server by placing it behind a reverse proxy or Esri Web Adaptor, limiting direct access to the REST endpoint from untrusted networks.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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