Security readout for executives and security teams
Plain-English summary
This flaw can let a remote, unauthenticated attacker force an affected Cisco IOS XE device to reload, causing a denial of service. The risk applies when Unified Threat Defense is configured and IPv6 traffic passes through the device. The bundle does not provide evidence of active exploitation.
Executive priority
Treat this as a high-priority availability risk for affected Cisco routing or security infrastructure. It does not indicate data theft or integrity compromise, but device reloads can interrupt business connectivity and security enforcement.
Technical view
CVE-2019-12657 is an improper validation issue in Cisco IOS XE Unified Threat Defense handling of IPv6 packets. Cisco describes remote, unauthenticated network exploitation against UTD-enabled devices, with successful exploitation causing device reload and loss of availability. CVSS is 8.6 high, with availability impact only.
Likely exposure
Organizations are likely exposed only where Cisco IOS XE devices, including the listed 3.16.0S software, have Unified Threat Defense configured and process IPv6 transit traffic.
Exploitation context
The source bundle says exploitation requires sending IPv6 traffic through an affected UTD-configured device. CISA KEV status is false, and no cited source in the bundle confirms active exploitation.
Researcher notes
Core conditions are UTD enabled, IPv6 traffic traversing the device, and affected Cisco IOS XE software. The bundle does not include fixed-release details or workaround text, so validation should be anchored to Cisco advisory cisco-sa-20190925-utd.
Mitigation direction
- Check Cisco's advisory for affected releases, fixed releases, and any supported workaround.
- Prioritize remediation for internet-facing or high-availability network edge devices using UTD.
- Review whether UTD is required on IPv6 traffic paths until vendor guidance is applied.
- Monitor affected devices for unexpected reloads or availability degradation.
- Plan change windows because remediation may require network device software updates.
Validation and detection
- Inventory Cisco IOS XE devices and record exact software versions.
- Confirm whether Unified Threat Defense is configured on each device.
- Identify devices forwarding IPv6 traffic through UTD-enabled paths.
- Compare findings against Cisco's advisory for this CVE.
- Review operational logs for reloads matching affected device exposure windows.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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Open ATT&CK lookupCVE-2019-12657 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 8.6 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H3.94Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.6HighVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20190925 Cisco IOS XE Software Unified Threat Defense Denial of Service VulnerabilityCVE reference · vendor-advisory, x_refsource_CISCO
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.