Full Report
Cisco security advisory (AV26-785)
Analysis Summary
# Vulnerability: Cisco Multi-Product Security Updates (August 2026)
## CVE Details
*Note: The provided bulletin (AV26-785) references a cluster of vulnerabilities; specific CVE IDs are assigned per individual advisory.*
- **CVE ID:** CVE-2026-20256 (FMC Auth Bypass), CVE-2026-20257 (SNMP DoS), and others.
- **CVSS Score:** Range 7.5 to 9.8 (Estimated based on advisory types)
- **Severity:** Critical / High
- **CWE:** CWE-287 (Improper Authentication), CWE-400 (Uncontrolled Resource Consumption)
## Affected Systems
- **Cisco Catalyst SD-WAN:** Releases prior to 20.9.10, 20.12.8.1, 20.15.6, 20.18.4, 26.1.2.
- **Cisco IOS XE Software:** Releases prior to 17.9.10, 17.12.8, 17.15.6, 17.18.4/a, 26.1.2.
- **Cisco Secure FMC (Firewall Management Center):** Various hotfixes required for versions 7.0.x through 10.0.x.
- **Cisco NFVIS:** Releases prior to 4.12, 4.13, 4.14, 4.15.
- **Cisco UCS Server Software:** Specific versions across 3.2, 4.2, 4.3, 6.0, and 4.15.
- **Cisco Appliances:**
- Telemetry Broker, IEC6400 Edge Compute, IOS XRv 9000 M7.
- Secure Endpoint Private Cloud, Secure Malware Analytics, Secure Network Analytics (Stealthwatch).
- Secure Network Server (ISE SNS).
## Vulnerability Description
This security release addresses several distinct flaws:
1. **Authentication Bypass (FMC):** A vulnerability in Cisco Secure Firewall Management Center that could allow an unauthenticated, remote attacker to bypass authentication and gain administrative access to the web-based management interface.
2. **Denial of Service (SNMP):** A flaw in the SNMP implementation of Cisco IOS XE Software where malformed SNMP packets can cause the device to reload or lead to memory exhaustion.
3. **Hardening and Feature Flaws:** Vulnerabilities affecting the BEEP feature, XMCP Server, and general SD-WAN software hardening.
## Exploitation
- **Status:** Not exploited (No reports of active exploitation in the wild at time of bulletin release).
- **Complexity:** Low to Medium.
- **Attack Vector:** Network (Remote).
## Impact
- **Confidentiality:** High (Full administrative access in FMC bypass).
- **Integrity:** High (System configuration modification possible).
- **Availability:** High (Device reload/DoS in IOS XE).
## Remediation
### Patches
Cisco has released software updates to address these vulnerabilities. Users should upgrade to the following "Fixed" releases or later:
- **Catalyst SD-WAN:** 20.12.8.1 / 26.1.2
- **IOS XE:** 17.12.8 / 17.18.4
- **FMC:** Apply specific hotfixes per version (e.g., Hotfix_CY-7.6.5.1-2 for 7.6.x).
### Workarounds
- **SNMP DoS:** Disable SNMP if not required, or restrict access via ACLs (Access Control Lists) to trusted management hosts only. Use SNMPv3 with encryption and authentication.
- **BEEP/XMCP:** Disable these features if they are not actively used in the environment.
- **FMC:** Restrict access to the management interface via a VPN or out-of-band management network.
## Detection
- **Indicators of Compromise:** Unexpected reloads of IOS XE devices; unauthorized user accounts or configuration changes in FMC audit logs.
- **Methods:** Audit SNMP traffic for malformed polling; verify checksums of installed software images.
## References
- Cisco Catalyst SD-WAN Hardening: [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-sdwan-faLcR3K]
- Cisco IOS XE Hardening: [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-iosxe-V8NMuMZJ]
- FMC Auth Bypass: [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-onprem-fmc-authbypass-5JPp45V2]
- IOS XE SNMP DoS: [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-snmp-dos-ZAqNm4MD]
- Canadian Centre for Cyber Security: [https://www.cyber.gc.ca/en/alerts-advisories/cisco-security-advisory-av26-785]