Cisco Catalyst SD-WAN Manager Hex Encoding
CVE-2026-76504 is a critical-severity improper handling of URL encoding (hex encoding) vulnerability in Cisco Catalyst SD-WAN Manager from Cisco, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Cisco Catalyst SD-WAN Manager versions: 20.1.12; 19.2.1; 18.4.4, and others listed below. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on September 30, 2026, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Catalyst Sd-wan Manager to 20.9.10.1 or 20.12.8.2 or 20.15.6.1 or 20.18.4.1, whichever matches your release line, or a later version.
- CISA's 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.
- Read the advisory on sec.cloudapps.cisco.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Cisco | Cisco Catalyst SD-WAN Manager | 20.1.12; 19.2.1; 18.4.4; 18.4.5; 20.1.1.1; 20.1.1; 19.3.0; 19.2.2; and 32 more ranges | Not stated |
| Cisco | Catalyst Sd-wan Manager | before 20.9.10.1; 20.12 up to, but not including, 20.12.8.2; 20.15 up to, but not including, 20.15.6.1; 20.18 up to, but not including, 20.18.4.1; 26.1 up to, but not including, 26.1.2.1; 26.2 | 20.9.10.1, 20.12.8.2, 20.15.6.1, 20.18.4.1, 26.1.2.1 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (cisco.com).
Official description
A vulnerability in the API session-based authentication management of Cisco Catalyst SD-WAN Manager could allow an unauthenticated, remote attacker to access an affected system with privileges of the admin user. This vulnerability is due to improper handling of URI encoding in an HTTP request, which allows the request to bypass an authentication rule that is intended to restrict access to a specific API endpoint. An attacker could exploit this vulnerability by sending a crafted HTTP request to the API of the affected system. A successful exploit could allow the attacker to bypass authentication and gain access to the API as the admin user.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Handling of URL Encoding (Hex Encoding)
The product does not properly handle when all or part of an input has been URL encoded.
How developers prevent this class of flaw
- Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names.
- Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
More Improper Handling of URL Encoding (Hex Encoding) vulnerabilities (CWE-177)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Record last changed materially (score, affected products, status or references).
- Deadline for US federal agencies to remediate, set by CISA.
References
Advisories
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-76504US Government Resource
Our coverage
Other vulnerabilities in Cisco Catalyst SD-WAN Manager
- 7.7 High severity
- 8.8 High severity
- 9.1 Critical severity
- 9.9 Critical severity
- 9.9 Critical severity
- 6.5 Medium severity
Recent Improper Handling of URL Encoding (Hex Encoding) vulnerabilities
- 7.5 High severity
- 8.1 High severity
- 9.1 Critical severity
- 9.1 Critical severity
- 9.8 Critical severity
- 8.4 High severity
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