Security readout for executives and security teams
Plain-English summary
This vulnerability can let an unauthenticated remote attacker knock the Cisco IOx HTTPS web server offline on affected devices. It does not indicate data theft or device takeover, but it can disrupt management or application access where IOx is exposed.
Executive priority
Treat as a high-priority availability risk for exposed industrial or edge devices. Prioritize internet-reachable or broadly reachable IOx deployments, then follow Cisco guidance for remediation.
Technical view
CVE-2019-12656 is a TLS implementation issue in the Cisco IOx application environment. Crafted TLS packets can cause the IOx web server to stop processing HTTPS requests. CVSS 3.0 is 7.5, network exploitable, low complexity, no privileges, no user interaction, with availability impact only.
Likely exposure
Exposure is most likely on Cisco platforms running the IOx application environment, including Cisco Industrial Routers Operating System Software, where the IOx HTTPS web server is reachable by untrusted networks.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. The vulnerability is still practical to abuse because the CVSS vector is unauthenticated, remote, low complexity, and targets availability.
Researcher notes
Evidence supports unauthenticated remote DoS against IOx HTTPS TLS handling. The bundle does not provide affected version granularity, fixed versions, workarounds, or exploitation telemetry beyond the Cisco advisory reference.
Mitigation direction
- Review Cisco’s advisory for affected releases and official fixed software guidance.
- Apply Cisco-supported updates or workarounds where the advisory identifies them.
- Restrict IOx HTTPS access to trusted administration networks only.
- Monitor affected devices for IOx HTTPS service failures or repeated TLS errors.
Validation and detection
- Inventory Cisco devices running the IOx application environment.
- Confirm whether Cisco Industrial Routers Operating System Software is present.
- Identify whether the IOx HTTPS web server is reachable from untrusted networks.
- Compare installed software versions against Cisco’s advisory.
- Check monitoring for IOx web server availability interruptions.
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-2019-12656 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/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:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
7.5HighVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20190925 Cisco IOx Application Environment 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.