High [CVE-2026-20230] Cisco Unified Communications Manager Server-Side Request Forgery Vulnerability
This high-severity Cisco advisory covers CVE-2026-20230 affecting Unified Communications Manager.
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Summary
A vulnerability in Cisco Unified Communications Manager (Unified CM) and Cisco Unified Communications Manager Session Management Edition (Unified CM SME) could allow an unauthenticated, remote attacker to conduct server-side request forgery (SSRF) attacks through an affected device.
This vulnerability is due to improper input validation for specific HTTP requests. An attacker could exploit this vulnerability by sending a crafted HTTP request to an affected device.
A successful exploit could allow the attacker to write files to the underlying operating system that could be used later to elevate to root.
Note: Cisco has assigned this security advisory a Security Impact Rating (SIR) of Critical rather than High as the score indicates. The reason is that exploitation of this vulnerability could result in an attacker elevating privileges to root.
Note: To exploit this vulnerability, the WebDialer service must be enabled. WebDialer is disabled by default.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
CISA Known Exploited Vulnerability
- Listed:
- Jun 25, 2026 · federal remediation due Jun 28, 2026
- Required action:
- Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
- Ransomware use:
- Unknown
KEV is a prioritization signal from CISA — remediation detail still comes from the vendor advisory.
- Scope: This vulnerability affects Cisco Unified CM and Unified CM SME if they have the WebDialer service enabled.
- Release 14 (first fixed: 14SU6)
- Release 15 (first fixed: 15SU5 (Sep 2026) or COP1)
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
- 14SU6
- 15SU5 (Sep 2026) or COP1
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
Mitigation checklist
- Upgrade to the first fixed release for your train per the Fixed Releases table in this advisory.
- Release 14: upgrade to 14SU6.
- Release 15: upgrade to 15SU5 (Sep 2026) or COP1.
- There are no workarounds that address this vulnerability. However, as a mitigation, administrators may disable the WebDialer service until a patch can be applied.
- To disable WebDialer, complete the following steps:
- Log in to the Cisco Unified CM Administration interface.
- From the Navigation menu, choose Cisco Unified Serviceability and click Go.
- From the Tools menu, choose Service Activation.
- In the CTI Services section of the page, uncheck the Cisco WebDialer Web Service check box and click Save.
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
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