CVE-2026-15546 Overview
CVE-2026-15546 is an operating system command injection vulnerability in Shibby Tomato firmware versions up to 1.28.0000. The flaw resides in the sub_2D568 function within the start_jffs2 component. Attackers can manipulate the jffs2_exec argument to inject arbitrary operating system commands. Remote exploitation is possible over the network, and a public exploit has been released. The Shibby Tomato project is no longer maintained and has been superseded by FreshTomato, meaning affected users must migrate rather than wait for a vendor patch.
Critical Impact
Remote attackers with low privileges can inject arbitrary operating system commands through the jffs2_exec argument, compromising router integrity on abandoned firmware.
Affected Products
- Shibby Tomato firmware up to and including version 1.28.0000
- The start_jffs2 component containing the sub_2D568 function
- Legacy routers running Shibby Tomato builds (project superseded by FreshTomato)
Discovery Timeline
- 2026-07-13 - CVE-2026-15546 published to NVD
- 2026-07-13 - Last updated in NVD database
Technical Details for CVE-2026-15546
Vulnerability Analysis
The vulnerability is classified as OS Command Injection under [CWE-77]. It exists in the sub_2D568 function of the start_jffs2 component in Shibby Tomato firmware. The component handles JFFS2 filesystem initialization on the router. When processing the jffs2_exec argument, the function passes attacker-controlled input to a shell interpreter without adequate sanitization. This allows injected shell metacharacters to break out of the intended command context and execute arbitrary operating system commands on the device.
Exploitation is network-reachable, requires low privileges, and does not require user interaction. Public exploit code has been released, increasing the likelihood of opportunistic exploitation against exposed devices. Because Shibby Tomato is no longer developed, no upstream patch will be produced.
Root Cause
The root cause is improper neutralization of special elements used in an OS command. The sub_2D568 routine concatenates the jffs2_exec argument into a command string executed by the shell. Shell metacharacters such as ;, |, &, and backticks are not filtered or escaped, so any value supplied to jffs2_exec is interpreted as executable shell syntax.
Attack Vector
An authenticated attacker with low-level privileges sends a crafted request that reaches the start_jffs2 handler and supplies a malicious payload in the jffs2_exec argument. The injected commands run in the context of the invoking process on the router. Because the exploit is public, automated scanners can weaponize it against internet-exposed management interfaces. Refer to the VulDB CVE-2026-15546 entry and the Gitee issue discussion for the disclosed technical details.
Detection Methods for CVE-2026-15546
Indicators of Compromise
- Unexpected shell processes spawned by the start_jffs2 service or its child processes on the router
- HTTP or management-interface requests containing shell metacharacters (;, |, &, `, $()) in parameters mapping to jffs2_exec
- Outbound network connections from the router to unfamiliar hosts following JFFS2 initialization events
- Modifications to persistent JFFS2 storage or startup scripts not initiated by an administrator
Detection Strategies
- Inspect router syslog and management-interface logs for anomalous jffs2_exec values containing command separators
- Deploy network intrusion detection signatures that flag command-injection payloads targeting Tomato-derived firmware
- Compare router firmware and configuration against known-good baselines to identify tampering
Monitoring Recommendations
- Forward router logs to a centralized log platform and alert on shell metacharacters in administrative parameters
- Monitor egress traffic from router management VLANs for connections to unexpected destinations
- Track authentication events on router management interfaces to detect low-privilege account abuse
How to Mitigate CVE-2026-15546
Immediate Actions Required
- Restrict router management interfaces to trusted internal networks and disable remote WAN administration
- Rotate all administrative credentials on affected devices to reduce low-privilege attacker access
- Migrate from Shibby Tomato to the actively maintained FreshTomato firmware as soon as feasible
- Audit deployed devices for indicators of prior compromise before migration
Patch Information
No official patch exists for Shibby Tomato because the project is discontinued. Shibby Tomato has been superseded by FreshTomato, and users should migrate to the current FreshTomato release. Consult the VulDB submission report for disclosure metadata.
Workarounds
- Place affected routers behind a network segment that blocks untrusted inbound access to management services
- Disable the JFFS2 feature in the router configuration if it is not required by the deployment
- Enforce administrative access through VPN only, eliminating direct exposure of the web management interface
- Replace end-of-life hardware or firmware where migration to FreshTomato is not supported
# Configuration example: restrict router management to a trusted subnet
# Replace 192.0.2.0/24 with your administrative network
iptables -I INPUT -p tcp --dport 80 -s 192.0.2.0/24 -j ACCEPT
iptables -I INPUT -p tcp --dport 80 -j DROP
iptables -I INPUT -p tcp --dport 443 -s 192.0.2.0/24 -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.
