WRT54GL: Improper Neutralization of Special Elements used in a Command
CVE-2026-121931 is a critical-severity improper neutralization of special elements used in a command vulnerability in WRT54GL from Linksys, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. Affected WRT54GL versions: 4.30.18. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 2.72% chance of exploitation within 30 days, higher than 86% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of WRT54GL you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- HighAdministrator-level access is required first.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H. Scored by CNA (vuldb.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.5 | High | CNA (vuldb.com) |
| CVSS 3.1 | 9.1 | Critical | CNA (vuldb.com) |
| CVSS 2.0 | 8.3 | High | CNA (vuldb.com) |
Official description
A security vulnerability has been detected in Linksys WRT54GL 4.30.18. The impacted element is the function system of the file apply.cgi of the component Traceroute Diagnostic Function. Such manipulation of the argument traceroute_ip leads to os command injection. The attack can be launched remotely. The exploit has been disclosed publicly and may be used. 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements used in a Command
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.
How developers prevent this class of flaw
- If at all possible, use library calls rather than external processes to recreate the desired functionality.
- If possible, ensure that all external commands called from the program are statically created.
- Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.
More Improper Neutralization of Special Elements used in a Command vulnerabilities (CWE-77)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in WRT54GL
- 9.1 Critical severity
- 7.5 High severity
Recent Improper Neutralization of Special Elements used in a Command vulnerabilities
- 9.9 Critical severity
- 10.0 Critical severity
- 7.3 High severity
- 10.0 Critical severity
- 7.2 High severity
- 7.8 High severity
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