CVE-2026-15547 Overview
CVE-2026-15547 is an OS command injection vulnerability affecting Shibby Tomato firmware up to version 1.28.0000. The flaw resides in the sub_2D048 function within the CIFS Mount Handler component. Attackers can manipulate the cifs1 or cifs2 arguments to inject arbitrary operating system commands. The vulnerability is exploitable remotely and requires low-level privileges on the target device. A public exploit has been disclosed, increasing the likelihood of opportunistic exploitation. The Shibby Tomato project is no longer actively maintained and has been superseded by FreshTomato. This weakness is categorized under CWE-77: Improper Neutralization of Special Elements used in a Command.
Critical Impact
Authenticated remote attackers can inject arbitrary OS commands through the CIFS mount handler, compromising affected Tomato routers.
Affected Products
- Shibby Tomato firmware versions up to and including 1.28.0000
- CIFS Mount Handler component (sub_2D048 function)
- Devices running end-of-life Shibby Tomato builds
Discovery Timeline
- 2026-07-13 - CVE-2026-15547 published to NVD
- 2026-07-13 - Last updated in NVD database
Technical Details for CVE-2026-15547
Vulnerability Analysis
The vulnerability exists in the sub_2D048 function of the CIFS Mount Handler in Shibby Tomato firmware. This handler processes CIFS (Common Internet File System) mount configuration parameters submitted through the router administration interface. The function fails to properly neutralize shell metacharacters in the cifs1 and cifs2 arguments before passing them to an underlying operating system command. As a result, an authenticated attacker can append arbitrary commands that execute in the context of the router firmware. Because Shibby Tomato has been superseded by FreshTomato, no upstream vendor patch is expected. Public proof-of-concept material referenced in the Gitee issue discussion and VulDB entry increases exposure for affected devices.
Root Cause
The root cause is improper neutralization of special elements passed to an OS command [CWE-77]. The sub_2D048 function concatenates user-controlled cifs1 and cifs2 values directly into a shell command string used to configure or mount CIFS shares. Without proper sanitization or argument separation, shell metacharacters such as backticks, semicolons, and pipes break out of the intended command context.
Attack Vector
The attack is executed over the network against the router's administrative interface. An attacker with low-privilege authenticated access submits crafted values in the cifs1 or cifs2 fields. When the CIFS mount handler processes these values, the injected commands execute with the privileges of the firmware process, typically root on embedded Tomato devices. The public availability of exploit details lowers the technical barrier for attackers to weaponize this flaw.
No verified proof-of-concept code is available for direct reproduction. Refer to the VulDB vulnerability record for further technical detail on the injection mechanism.
Detection Methods for CVE-2026-15547
Indicators of Compromise
- Unexpected child processes spawned by the router HTTP administration daemon following requests that modify CIFS mount settings.
- Outbound network connections from the router to unfamiliar hosts shortly after CIFS configuration changes.
- Unauthorized modifications to NVRAM variables related to cifs1 or cifs2 containing shell metacharacters such as ;, |, `, or $().
Detection Strategies
- Inspect router HTTP request logs for POST parameters targeting the CIFS configuration endpoint containing shell metacharacters in cifs1 or cifs2 fields.
- Review firmware syslog output for unexpected shell invocations linked to the mount handler execution path.
- Correlate administrative authentication events with subsequent configuration changes to detect misuse of low-privilege accounts.
Monitoring Recommendations
- Forward router syslog output to a central log platform for retention and analysis of configuration and process events.
- Enable network traffic monitoring on the router management VLAN to identify anomalous outbound connections originating from the device.
- Alert on any changes to CIFS-related NVRAM parameters outside approved change windows.
How to Mitigate CVE-2026-15547
Immediate Actions Required
- Migrate affected devices from Shibby Tomato to the actively maintained FreshTomato firmware, which supersedes the abandoned project.
- Restrict access to the router administrative interface to trusted management networks only, disabling remote WAN administration.
- Rotate all router administrative credentials and disable any unused low-privilege accounts that could be leveraged for exploitation.
Patch Information
No vendor patch is available. The Shibby Tomato project is no longer maintained and has been superseded by FreshTomato. Users should replace affected firmware with a supported alternative build that addresses this class of command injection issue. Consult the VulDB CVE-2026-15547 entry for the current advisory status.
Workarounds
- Disable the CIFS client feature in the router configuration if it is not required for operational use.
- Segment the router management interface behind a firewall or VPN so only administrators can reach the CIFS configuration pages.
- Audit and remove unnecessary administrative accounts to reduce the population of users who could invoke the vulnerable handler.
# Example: restrict router admin access to a trusted management subnet
# (adapt to the specific Tomato admin interface controls)
iptables -I INPUT -p tcp --dport 80 -s 10.0.0.0/24 -j ACCEPT
iptables -I INPUT -p tcp --dport 80 -j DROP
iptables -I INPUT -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -I INPUT -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
