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KEV catalog · CISA Known Exploited Vulnerabilities

CVE-2026-76504 9.8
Cisco · Catalyst SD-WAN Manager · Added 2026-09-30 · Published 2026-09-30
3-Day Required KEV Automatable Active Exploitation

Details

VulnerabilityCisco Catalyst SD-WAN Manager Hex Encoding Vulnerability
VendorCisco
ProductCatalyst SD-WAN Manager
Date added2026-09-30
Due date2026-10-03
Required actionApply 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.
CWECWE-177
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Descriptions

KEV: Cisco Catalyst SD-WAN Manager contains a hex encoding vulnerability that could allow an unauthenticated, remote attacker to access an affected system with privileges of the admin user due to improper handling of URI encoding in an HTTP request.

NVD: 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.

Compliance SSVC + BOD 26-04

Automatableyes
Technical impacttotal
Exploitation statusactive
3-day qualifyingYes
Public timeline3 days + forensic
Non-public timeline3 days + forensic
Forensic (public)Required
Forensic (non-public)Required

Research metadata

Last researched2026-09-30 22:47 UTC
Wall time0.5s
Searches10
Component defaultyes

QC notes

info precondition_contradiction: Preconditions don't mention deployment applicability (component/product version)

Hunting hypothesis agent

Hunt serviceproxy-access.log for POST /%6a_security_check requests to Catalyst SD-WAN Manager from unknown IPs and vmanage-server.log for j_security_check entries with viptela-reserved- users showing hex-encoding auth bypass.

Research details

Componentservice-proxy API session authentication - j_security_check login endpoint (hex URI-encoding bypass, e.g. POST /%6a_security_check)
PreconditionsUnauthenticated remote attacker with HTTP(S) network reachability to the vManage service-proxy API; no credentials or user interaction required. Affects every release before these fixes: migrate if earlier than 20.9, otherwise 20.9 < 20.9.10.1, 20.12 < 20.12.8.2, 20.15 < 20.15.6.1, 20.18 < 20.18.4.1, 26.1 < 26.1.2.1, 26.2 < 26.2.1; Cisco-managed SD-WAN Cloud fixed in release 20.15.605. agent
Deliveryunauthenticated crafted HTTP request to the service-proxy API that hex-encodes a character of the j_security_check URI path (e.g. POST /%6a_security_check)
Public PoCno
Exploit notesCVSS attack complexity: LOW | CRITICAL severity (CVSS >= 9.0). Unauthenticated hex-encoding bypass of the authentication rule on the j_security_check login path - any single URI-encoded character works (Cisco IOC example: POST /%6a_security_check). Cisco PSIRT observed active exploitation in September 2026, discovered via a TAC support case. A GitHub repository (ShadowForge-Cyber/CVE-2026-76504-Proof-of-concept) advertises an exploit but contains only a README with no code, so no reproducible public PoC is available.
SummaryCisco Catalyst SD-WAN Manager fails to normalize hex-encoded characters in the API session login URI, letting an unauthenticated remote attacker bypass the authentication rule on j_security_check and use the API as admin (CVSS 9.8, CWE-177). Cisco PSIRT reports active exploitation as of September 2026 and has issued fixed releases on all supported trains, with no workarounds available. CISA added the issue to the KEV catalog on 2026-09-30 with a 2026-10-03 due date and forensic-triage requirements. No functional public PoC has been published.

Tia coverage

First reported2026-06-05
First exploit report2026-09-30
Exploit report → KEV0 days before the listing

When Tia's reporting first covered this CVE and whether a report claimed exploitation before the KEV listing. Lead-time deltas are measured from the exploitation report only — plain coverage is not exploitation intel. See the story links under Mentioned in for coverage detail.

Mentioned in

cisco-sd-wan-manager-auth-bypass-cve-2026-76504-cvss-9-8-under-e

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Source on GitHub