Sources: National Vulnerability Database, CVE.org, CISA KEV, FIRST EPSS
CVE-2026-121930 Overview
A weakness has been identified in Linksys WRT54GL 4.30.18. The affected element is the function system of the file apply.cgi of the component Ping Diagnostic. This manipulation of the argument ping_ip causes os command injection. The attack can be initiated remotely. The exploit has been made available to the public and could be used for attacks. 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 WRT54GL: see the vendor advisory for the exact affected versions
Discovery Timeline
- 2026-11-04: CVE-2026-121930 published to the National Vulnerability Database by cna@vuldb.com
- 2026-11-04: last updated in the NVD database
Technical Details for CVE-2026-121930
Vulnerability Analysis
CVE-2026-121930 is a Command Injection weakness (CWE-77: Command Injection, CWE-78: OS Command Injection) in Linksys WRT54GL. Based on its CVSS vector, the flaw can be reached over the network, needs some level of access, and needs no user interaction. Untrusted input ends up inside a system command.
With a CVSS base score of 8.5, apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Root Cause
The weakness is classified as CWE-77: Command Injection, CWE-78: OS Command Injection. Untrusted input ends up inside a system command.
Attack Vector
Based on the CVSS vector, the flaw can be reached over the network, needs some level of access, 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:H/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-2026-121930
Detection Strategies
- Inventory every instance of Linksys WRT54GL 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 WRT54GL 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-2026-121930
Immediate Actions Required
- Apply the fixed version of Linksys WRT54GL 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 WRT54GL.
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-77: Command Injection More CVEs with this weakness
- CWE-78: OS Command Injection 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.
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