CVE-2026-27850Public exploitNetwork attack vector

LAN service exposure via trusted source port

Published Feb 25, 2026 · Updated Feb 25, 2026

Improper source verification in Linksys MR9600 1.0.4.205530 and MX4200 1.0.13.210200 allows remote attackers to reach LAN-only services. The wan2self_ports iptables chain accepts every TCP packet arriving on WAN interface eth0 when its source port is 5222, regardless of destination port. This requires no authentication and exposes services bound to all interfaces, including a demonstrated command-injection service, unless another firewall blocks access.

CVSS severity7.5
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper source verification in Linksys MR9600 1.0.4.205530 and MX4200 1.0.13.210200 allows remote attackers to reach LAN-only services. The wan2self_ports iptables chain accepts every TCP packet arriving on WAN interface eth0 when its source port is 5222, regardless of destination port. This requires no authentication and exposes services bound to all interfaces, including a demonstrated command-injection service, unless another firewall blocks access.

The record

CVE
CVE-2026-27850
Published
Feb 25, 2026
Updated
Feb 25, 2026
Vendor
Linksys
Product
MX4200
Classifications
CWE-940, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 25, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.0.13.210200

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Linksys · MX4200version=1.0.13.210200
Linksys · MR9600version=1.0.4.205530

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-940Improper Verification of Source of a Communication Channel
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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