LAN Telnet enablement via undocumented backdoor
Published Mar 27, 2026 · Updated Mar 27, 2026
Hidden functionality in NEC Platforms Aterm Series routers allows remote attackers on the LAN to enable Telnet through a backdoor. An undocumented backdoor function accepts a network trigger and turns on the Telnet service, but NEC has not published the trigger, endpoint, or code locus. The gate is LAN-side access rather than WAN-side Internet reachability; NEC has not disclosed what access the enabled Telnet service grants.
Summary
What happened
Hidden functionality in NEC Platforms Aterm Series routers allows remote attackers on the LAN to enable Telnet through a backdoor. An undocumented backdoor function accepts a network trigger and turns on the Telnet service, but NEC has not published the trigger, endpoint, or code locus. The gate is LAN-side access rather than WAN-side Internet reachability; NEC has not disclosed what access the enabled Telnet service grants.
The record
- CVE
- CVE-2026-4621
- Published
- Mar 27, 2026
- Updated
- Mar 27, 2026
- Vendor
- NEC Platforms, Ltd.
- Product
- Aterm WG2600HM4
- Classifications
- CWE-912
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 27, 2026CVE publishedPublication date reported by the CVE source.
- Mar 27, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=Before Ver. 1.4.2
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What is affected?
Published CVSS scores
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Attacks
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Weakness, pattern, technique
Public exploit references
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Technologies
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Your stack
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