Security readout for executives and security teams
Plain-English summary
This flaw can make an affected Cisco IOS XE device reload when it inspects certain FTP traffic passing through NAT, NAT64, or zone-based firewall functions. The business impact is network interruption, not documented data theft. Remote attackers do not need credentials, so exposed transit devices deserve prompt review.
Executive priority
High priority for network edge or transit infrastructure because a successful attack can interrupt connectivity by reloading the device. The urgency rises where FTP traffic from untrusted networks crosses Cisco IOS XE NAT, NAT64, or ZBFW inspection paths.
Technical view
CVE-2019-12655 is a buffer-overflow denial-of-service issue in Cisco IOS XE FTP ALG inspection used by NAT, NAT64, and ZBFW. A specific FTP transfer through an affected device can trigger a reload. CVSS 3.0 is 8.6 with network attack vector, low complexity, no privileges, and high availability impact.
Likely exposure
Exposure is most likely on Cisco IOS XE devices running the affected release and configured to inspect FTP traffic through NAT, NAT64, or ZBFW. The bundle names Cisco IOS XE Software 3.16.8S; broader affected-release details should be confirmed against Cisco guidance.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation. Exploitation requires FTP traffic to traverse an affected inspection path, but the public description does not provide enough evidence to assess real-world exploitation prevalence.
Researcher notes
Evidence supports unauthenticated remote DoS via FTP ALG inspection and CWE-20 classification. The bundle does not include exploit code, fixed-release tables, or active exploitation evidence. Avoid expanding affected versions beyond Cisco’s advisory and CVE records.
Mitigation direction
- Review Cisco’s advisory for fixed releases and official remediation guidance.
- Prioritize upgrades or vendor-approved remediation for exposed transit devices.
- Limit untrusted FTP traffic through affected NAT, NAT64, or ZBFW paths where operationally feasible.
- Monitor for unexpected IOS XE reloads until remediation is complete.
Validation and detection
- Inventory Cisco IOS XE devices and confirm software release information.
- Identify devices using NAT, NAT64, or ZBFW with FTP inspection paths.
- Check whether any device runs Cisco IOS XE Software 3.16.8S or advisory-listed affected releases.
- Review operational logs for unexplained reloads correlated with FTP traffic.
- Confirm remediation status against Cisco’s advisory, not assumptions.
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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CWE-20: Exact CWE lookup
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Open ATT&CK lookupCVE-2019-12655 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
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 FTP Application Layer Gateway for NAT, NAT64, and ZBFW 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.