# CVE-2026-102484: NTPsec ntpd heap buffer overflow in JJY refclock driver

Source: https://junglewise.ai/threats/cve-2026-102484-heap-based-buffer-overflow-in-the-jjy-refclock-driver-in-ntpsec  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-21. Updated: 2026-10-21  
License: CC BY 4.0 with a link back

CVE-2026-102484 · Severity: medium · CVSS 6.4 · Published 2026-10-21

NTPsec's ntpd is a network time synchronization daemon that coordinates time across systems. A heap-based buffer overflow in its JJY refclock driver allows an attacker who controls the Telephone JJY time source to crash ntpd or corrupt memory by sending more than six malformed time replies. This can disrupt time synchronization services or potentially lead to code execution.

Technologies: [Ntpsec Ntpd](https://junglewise.ai/threats/technologies/ntpsec-ntpd). Vendors: [Ntpsec](https://junglewise.ai/threats/vendors/ntpsec).

## Quick answers

**Is CVE-2026-102484 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-102484 being exploited in the wild.

**How severe is CVE-2026-102484?** Medium severity, with a CVSS score of 6.4, published 21 October 2026.

**Which products and versions are affected?** Ntpsec Ntpd before 1.2.6.

**Is there a fix for CVE-2026-102484?** Yes: fixed in ntpd 1.2.6. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-102484 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-102484?** Check whether you run Ntpsec Ntpd 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 ntpd 1.2.6

## Technical details

The vulnerability is a heap-based buffer overflow in ntpd/refclock_jjy.c where the iTimestampCount variable could overflow when processing time replies from a JJY time source, exceeding the MAX_TIMESTAMP array bounds. An attacker controlling the Telephone JJY time source can trigger the overflow by sending more than six time replies, corrupting adjacent heap memory and crashing the ntpd process. The fix converts iTimestampCount to unsigned and adds bounds checking before incrementing the array index.

## Affected products

- NTPsec ntpd before 1.2.6

## Timeline

- 2026-10-21: disclosed
- 2026-09-29: patched: Fix commit 62a454f6 authored by Gary E. Miller

## References

- [https://gitlab.com/NTPsec/ntpsec/-/commit/62a454f6fcb6f2dcc8d5866f6558905ebdb7dd69](https://gitlab.com/NTPsec/ntpsec/-/commit/62a454f6fcb6f2dcc8d5866f6558905ebdb7dd69)
- [https://gitlab.com/NTPsec/ntpsec/-/work_items/895](https://gitlab.com/NTPsec/ntpsec/-/work_items/895)

## Related threats

- [NTPsec ntpd out-of-bounds read in NTS extension parsing](https://junglewise.ai/threats/cve-2026-102486-out-of-bounds-read-in-nts-extension-field-parsing-in-ntpsec-ntpd)
- [NTPsec ntpd out-of-bounds read in Motorola Oncore driver](https://junglewise.ai/threats/cve-2026-102485-out-of-bounds-read-in-the-motorola-oncore-refclock-driver-in)
- [NTPsec ntpd denial of service in NTS Cookie handling](https://junglewise.ai/threats/cve-2026-102483-reachable-exit-in-ntpsec-ntpd-1-1-4-through-1-2-5-allows-a)