Security readout for executives and security teams
Plain-English summary
Affected NEC UNIVERGE IX-R/IX-V devices may let an internet-based attacker bypass WebGUI login controls and run administrative CLI commands. This could enable device takeover, configuration changes, traffic disruption, or exposure of information handled by the device. No user action or existing account is required.
Executive priority
Treat internet-reachable affected devices as an immediate remediation priority. Isolate their management interfaces, investigate for suspicious changes, and obtain NEC's supported remediation. Internally restricted devices still require prompt inventory and correction because compromised internal access could reach the same flaw.
Technical view
CVE-2026-16876 is a CWE-306 authentication bypass in the WebGUI. Tampered WebGUI messages can reportedly reach arbitrary CLI command execution over the network. CVSS 4.0 rates it 9.3: low complexity, no privileges or interaction, with high confidentiality and integrity impact and low availability impact.
Likely exposure
Exposure is highest where an affected device's WebGUI is reachable from the internet or untrusted networks. Listed affected releases are Ver1.1 through Ver1.3, Ver1.4.21 through Ver1.4.28, and Ver1.5.23. The bundle does not establish whether WebGUI access is enabled by default.
Exploitation context
The supplied sources do not establish active exploitation or a public proof of concept, and the CVE is not identified as KEV. Nevertheless, network reachability, absent authentication, low attack complexity, and arbitrary CLI execution make exposed devices urgent targets for defensive action.
Researcher notes
The provided record attributes exploitation to tampered WebGUI messages but does not document protocol details, affected endpoints, default exposure, indicators, or a confirmed fix. Avoid assuming unaffected versions beyond the enumerated ranges. Validation should remain non-destructive and focus on firmware, reachability, logs, configuration integrity, and vendor guidance.
Mitigation direction
- Remove affected WebGUI interfaces from direct internet exposure immediately.
- Restrict management access to trusted administrative networks and authorized operators.
- Check NEC's advisory for supported fixed firmware or vendor-prescribed mitigations.
- Apply the vendor-supported remediation after testing and preserve current configurations for recovery.
- Monitor affected devices for unauthorized administrative or configuration activity.
Validation and detection
- Inventory UNIVERGE IX-R/IX-V models and record their exact firmware versions.
- Identify whether each WebGUI is reachable from internet or untrusted network segments.
- Review device logs and configuration histories for unexplained administrative changes or CLI activity.
- Confirm installed firmware and remediation status against NEC's published advisory.
- After remediation, verify unauthenticated clients cannot access WebGUI administrative functions.
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-306: Credential and account abuse lookup
Authentication and credential weaknesses can make valid-account abuse and credential telemetry useful review starting points. 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 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-2026-16876 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
- 9.3 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
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.
SSVC decision data
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:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N——NECVulnerability scoring details
Base CVSS 4.0 score
9.3CriticalVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://jpn.nec.com/security-info/secinfo/nv26-005_en.htmlCVE reference, NEC
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.
Missing Authentication for Critical Function
Missing Authentication for Critical Function represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.