# CVE-2026-78403: Thales Sentinel Keys Server stack-based buffer overflow

Source: https://junglewise.ai/threats/cve-2026-78403-stack-based-buffer-overflow-and-missing-authorization  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-30. Updated: 2026-10-30  
License: CC BY 4.0 with a link back

CVE-2026-78403 · Severity: critical · CVSS 9.8 · Published 2026-10-30

Thales Sentinel Keys Server is a cryptographic key management appliance used to protect sensitive encryption keys in enterprise environments. An unvalidated HTTP request field can trigger a stack-based buffer overflow, allowing an attacker to execute arbitrary code with system privileges (NT AUTHORITY\SYSTEM) and gain complete control over the key management infrastructure.

Vendors: [Thales](https://junglewise.ai/threats/vendors/thales).

## Quick answers

**Is CVE-2026-78403 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-78403 being exploited in the wild.

**How severe is CVE-2026-78403?** Critical severity, with a CVSS score of 9.8, published 30 October 2026.

**Which products and versions are affected?** Thales Sentinel Keys Server below 1.3.8.0.

**Is there a fix for CVE-2026-78403?** Yes: fixed in 1.3.8.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-78403 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-78403?** Check whether you run Thales Sentinel Keys Server 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 1.3.8.0

## Technical details

A stack-based buffer overflow in Thales Sentinel Keys Server occurs due to missing length validation of the first field in HTTP requests; an unauthenticated attacker can send a crafted HTTP request over the network to trigger the overflow and achieve remote code execution with NT AUTHORITY\SYSTEM privileges. The vulnerability affects versions prior to 1.3.8.0 and requires no user interaction or prior authentication.

## Affected products

- Thales Sentinel Keys Server below 1.3.8.0

## Timeline

- 2026-10-30: disclosed

## References

- [https://supportportal.thalesgroup.com/csm?id=kb_article_view&sys_kb_id=50fc9f3b3b005f10bba8b41864e45a61&sysparm_article=KB0031216](https://supportportal.thalesgroup.com/csm?id=kb_article_view&sys_kb_id=50fc9f3b3b005f10bba8b41864e45a61&sysparm_article=KB0031216)

## Related threats

- [Thales Sentinel Keys Server stack-based buffer overflow](https://junglewise.ai/threats/cve-2026-78402-stack-based-buffer-overflow-and-out-of-bounds-write-vulnerability)