# CVE-2025-62839: QNAP Hybrid Backup Sync hard-coded cryptographic key

Source: https://junglewise.ai/threats/cve-2025-62839-an-use-of-hard-coded-cryptographic-key-vulnerability-has-been  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-29. Updated: 2026-10-29  
License: CC BY 4.0 with a link back

CVE-2025-62839 · Severity: info · Published 2026-10-29

Hybrid Backup Sync, a backup and recovery application for QNAP NAS systems, contains a hard-coded cryptographic key that could allow attackers to compromise encrypted backup data. An attacker exploiting this flaw could decrypt backups, access sensitive files, or potentially gain unauthorized access to the system by bypassing security protections.

Technologies: [QNAP Hybrid Backup Sync](https://junglewise.ai/threats/technologies/hybrid-backup-sync). Vendors: [QNAP](https://junglewise.ai/threats/vendors/qnap).

## Quick answers

**Is CVE-2025-62839 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-62839 being exploited in the wild.

**How severe is CVE-2025-62839?** Informational severity, published 29 October 2026.

**Which products and versions are affected?** QNAP HBS 3 Hybrid Backup Sync before 26.4.0.521; QNAP Hybrid Backup Sync before 26.4.1.563.

**Is there a fix for CVE-2025-62839?** Yes: fixed in HBS 3 Hybrid Backup Sync 26.4.0.521 and later, Hybrid Backup Sync 26.4.1.563 and later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2025-62839 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2025-62839?** Check whether you run QNAP HBS 3 Hybrid Backup Sync or QNAP Hybrid Backup Sync 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.

## How to fix

- Fixed in HBS 3 Hybrid Backup Sync 26.4.0.521 and later, Hybrid Backup Sync 26.4.1.563 and later

## Technical details

The vulnerability is a use of hard-coded cryptographic key flaw in QNAP's Hybrid Backup Sync application. An unauthenticated remote attacker with network access can exploit this weakness to compromise the confidentiality of encrypted backup data. The fix is available in patched versions.

## Affected products

- QNAP HBS 3 Hybrid Backup Sync before 26.4.0.521
- QNAP Hybrid Backup Sync before 26.4.1.563

## Timeline

- 2026-10-29: disclosed

## References

- [https://www.qnap.com/en/app-release-notes?keyword=HBS%203&app=HybridBackup&product-line=nas](https://www.qnap.com/en/app-release-notes?keyword=HBS%203&app=HybridBackup&product-line=nas)
- [https://www.qnap.com/en/app-release-notes?keyword=Hybrid&app=HybridBackup&product-line=nas](https://www.qnap.com/en/app-release-notes?keyword=Hybrid&app=HybridBackup&product-line=nas)

## Related threats

- [QNAP Hybrid Backup Sync hard-coded cryptographic key](https://junglewise.ai/threats/cve-2025-62841-an-use-of-hard-coded-cryptographic-key-vulnerability-has-been)
- [QNAP HBS 3 Hybrid Backup Sync path traversal](https://junglewise.ai/threats/cve-2025-62842-qnap-hbs-3-hybrid-backup-sync-path-traversal)
- [A generation of error message containing sensitive information vulnerability has been reported to affect HBS 3 Hybrid…](https://junglewise.ai/threats/cve-2025-62840-a-generation-of-error-message-containing-sensitive-information)