Sources: National Vulnerability Database, CVE.org, CISA KEV, FIRST EPSS
CVE-2026-121615 Overview
A vulnerability was determined in Linksys E5600 1.1.0.26. Affected is an unknown function of the file /cgi-bin/mesh_login.cgi of the component Login Handler. Executing a manipulation can lead to improper authentication. The attack can be launched remotely. The exploit has been publicly disclosed and may be utilized. The vendor was contacted early about this disclosure but did not respond in any way. This vulnerability only affects products that are no longer supported by the maintainer.
Critical Impact
Affected Products
- Linksys E5600: see the vendor advisory for the exact affected versions
Discovery Timeline
- 2026-11-04: CVE-2026-121615 published to the National Vulnerability Database by cna@vuldb.com
- 2026-11-04: last updated in the NVD database
Technical Details for CVE-2026-121615
Vulnerability Analysis
CVE-2026-121615 is a Improper Authentication weakness (CWE-287: Improper Authentication) in Linksys E5600. Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. The software does not properly prove who a user is.
With a CVSS base score of 9.3, apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Root Cause
The weakness is classified as CWE-287: Improper Authentication. The software does not properly prove who a user is.
Attack Vector
Based on the CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Attack complexity is low complexity.
No exploitation in the wild is confirmed by CISA at the time of the last update. Check the references below for any vendor or researcher proof of concept.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Detection Methods for CVE-2026-121615
Detection Strategies
- Inventory every instance of Linksys E5600 and compare the running version with the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Run an authenticated vulnerability scan once your scanner ships a check for this CVE.
Monitoring Recommendations
- Forward Linksys E5600 application, access and audit logs to your SIEM for retrospective hunting.
- Alert on new processes, configuration changes or outbound connections from the affected service.
- Track the vendor advisory and the CISA KEV catalog for changes in exploitation status.
How to Mitigate CVE-2026-121615
Immediate Actions Required
- Apply the fixed version of Linksys E5600 named in the vendor advisory.
- Prioritize internet facing and business critical instances first.
- Rescan after the change to confirm the exposure is closed.
Patch Information
Use the fixed version listed in the vendor advisory for Linksys E5600.
Workarounds
- If patching must wait, restrict network access to the affected service and place it behind authentication or a web application firewall rule.
CWE References
- CWE-287: Improper Authentication More CVEs with this weakness
Technical References
This entry is built directly from NVD, CISA KEV and EPSS data. Verify fixed versions in the vendor advisory before you deploy.
Frequently asked questions
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