Security readout for executives and security teams
Plain-English summary
CVE-2021-40112 covers multiple critical flaws in Cisco Catalyst PON Series ONT management. An unauthenticated remote attacker could gain access through default credentials when Telnet is enabled, inject commands, or alter device configuration. For executives, this is urgent because compromised ONT devices can affect network confidentiality, integrity, and availability.
Executive priority
Treat as immediate priority for any exposed Cisco Catalyst PON ONT environment. A successful attacker could take administrative actions remotely and disrupt or manipulate access network devices. If assets are internal-only and Telnet is disabled, urgency remains high but validation should drive sequencing.
Technical view
The vulnerability set affects the web-based management interface of Cisco Catalyst Passive Optical Network Series Optical Network Terminals. CVSS 3.1 is 10.0 with network attack vector, low complexity, no privileges, and no user interaction. The listed weakness is CWE-284, improper access control.
Likely exposure
Exposure is most likely where Cisco Catalyst PON Series ONT management interfaces are reachable from untrusted networks, or Telnet remains enabled. The source bundle does not provide specific affected version ranges, so teams must confirm product presence and software status against Cisco guidance.
Exploitation context
The bundle does not cite CISA KEV listing or active exploitation. However, the vendor-described impact includes unauthenticated remote access, command injection, and configuration modification, making reachable management interfaces high-risk even without confirmed exploitation evidence.
Researcher notes
Evidence supports critical severity and unauthenticated remote impact, but the provided bundle lacks fixed-version details, proof-of-concept status, and observed exploitation reports. Avoid assuming exploit availability. Focus validation on product presence, management-plane reachability, Telnet state, credential hygiene, and Cisco advisory alignment.
Mitigation direction
- Review Cisco advisory for affected software and fixed-release guidance.
- Disable Telnet where operationally possible.
- Remove default credentials and enforce unique administrative credentials.
- Restrict management interfaces to trusted administration networks only.
- Prioritize remediation for internet-reachable or provider-edge deployments.
Validation and detection
- Inventory Cisco Catalyst PON Series ONT assets.
- Identify management interfaces exposed beyond trusted networks.
- Check whether Telnet is enabled on affected devices.
- Verify default credentials are not accepted.
- Confirm installed software against Cisco advisory guidance.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-284: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-40112 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
- Critical
- CVSS
- 10 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/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:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H3.96Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
10CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20211103 Cisco Catalyst PON Series Switches Optical Network Terminal VulnerabilitiesCVE 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 Access Control
Improper Access Control represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.