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Memory Buffer Bounds ErrorWeakness · CWE-119

CVE-2026-15544

HIGH · 8.8 CVSS v3.1 Published 2026-07-13
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable Zero-click 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A vulnerability was determined in Shibby Tomato up to 1.28.0000. Affected is the function getupsvar of the file www/apcupsd/tomatodata.cgi of the component apcupsd. This manipulation of the argument Field causes stack-based buffer overflow. The attack may be initiated remotely. The exploit has been publicly disclosed and may be utilized. This project is superseded by FreshTomato.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Stack-based buffer overflow in the getupsvar function of www/apcupsd/tomatodata.cgi in Shibby Tomato firmware up to 1.28.0000. The 'Field' argument is not properly bounds-checked before being used in a stack buffer, allowing remote attackers to overwrite return addresses and potentially execute arbitrary code via crafted HTTP requests to the apcupsd web interface.

MitigationUpgrade to FreshTomato (the supported successor to Shibby Tomato) if available for the affected device, or implement input length validation on the Field argument in the getupsvar function and rebuild the firmware. Apply network segmentation to limit exposure to the web interface.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm Shibby Tomato firmware is running
    Access the router's web interface or check the system info page to identify the firmware name. Look for 'Shibby Tomato' or 'Tomato' in the firmware identification.
    Affected if The device is running Shibby Tomato firmware (any variant).
  2. Check firmware version against affected range
    Navigate to the firmware's version or status page. Locate the firmware version number displayed (e.g., shown as '1.28' or '1.28.0000' or similar). Compare this version to the affected range of 'all versions up to and including 1.28.0000'.
    Affected if The installed firmware version is 1.28.0000 or any version lower than 1.28.0000.
  3. Verify apcupsd module is enabled
    Check the router's web interface for UPS monitoring settings or apcupsd configuration. Look for 'UPS monitoring', 'APC UPS', or 'apcupsd' in the web UI menus or in /etc/httpd.conf if CLI access is available.
    Affected if The apcupsd UPS monitoring feature is enabled and accessible via the web interface.
  4. Confirm tomatodata.cgi is present and accessible
    Attempt to access the CGI script via HTTP. The vulnerability exists in 'www/apcupsd/tomatodata.cgi'. Try accessing http://<router-ip>/tomatodata.cgi or /apcupsd/tomatodata.cgi to verify the script exists and responds.
    Affected if The apcupsd web interface and tomatodata.cgi script are accessible on the network.

The environment is affected if the device runs Shibby Tomato firmware version 1.28.0000 or lower with the apcupsd web interface and tomatodata.cgi script enabled and accessible.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to FreshTomato (the supported successor to Shibby Tomato) if available for the affected device, or implement input length validation on the Field argument in the getupsvar function and rebuild the firmware. Apply network segmentation to limit exposure to the web interface.

Recommended fix High confidence

FreshTomato (latest stable release)

  1. Check the current Shibby Tomato firmware version in the router administration page.
  2. Obtain the latest FreshTomato firmware from the official FreshTomato project (e.g., from the FreshTomato downloads page).
  3. Back up the router’s current configuration or note any custom settings.
  4. Log into the router’s web interface as an administrator.
  5. Navigate to Administration > Firmware Upgrade and upload the FreshTomato firmware image.
  6. Apply the upgrade and allow the router to reboot.
  7. After reboot, verify the firmware version shows FreshTomato.
  8. Reapply any custom settings, especially those related to apcupsd, or disable the apcupsd functionality if not needed.
Caveat Upgrading may reset router configuration; restore custom settings after flashing.

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-15544 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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