# CVE-2026-45225: Heym path traversal in file upload endpoint

Source: https://junglewise.ai/threats/cve-2026-45225-heym-path-traversal-in-file-upload-endpoint  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-12. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

CVE-2026-45225 · Severity: high · CVSS 7.6 · Published 2026-05-12

Heym, an open-source tool, contains a security flaw in how it handles file uploads. An authenticated user can bypass intended storage limits to write, read, or delete files anywhere on the server's filesystem. This could allow an attacker to corrupt application data, overwrite critical system files, or potentially gain further control over the server.

Technologies: [Heymrun Heym](https://junglewise.ai/threats/technologies/heym). Vendors: [Heymrun](https://junglewise.ai/threats/vendors/heymrun).

## Quick answers

**Is CVE-2026-45225 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-45225 being exploited in the wild.

**How severe is CVE-2026-45225?** High severity, with a CVSS score of 7.6, published 12 May 2026.

**Which products and versions are affected?** Heymrun Heym < 0.0.21.

**Is there a fix for CVE-2026-45225?** A patch was published on 2026-05-10: Fix merged in PR #92 and released in v0.0.21 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-45225 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-45225?** Check whether you run Heymrun Heym at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A path traversal vulnerability exists in Heym's file upload mechanism due to insufficient validation of the 'filename' parameter in the multipart upload flow. The 'upload_file()' handler in 'backend/app/api/files.py' passes the client-provided filename directly to storage helpers, which construct filesystem paths using simple string interpolation without normalization. By using traversal sequences (e.g., '../'), an authenticated attacker can escape the designated storage root to perform unauthorized file writes, reads, or deletions. The vulnerability is fixed in version 0.0.21 by implementing strict filename validation and resolved-path containment checks in the storage layer.

## Affected products

- heymrun heym < 0.0.21

## Timeline

- 2026-05-10: patched: Fix merged in PR #92 and released in v0.0.21
- 2026-05-12: advisory: VulnCheck advisory published
- 2026-05-12: disclosed: CVE-2026-45225 published

## References

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

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