# CVE-2026-18321: ntpsec: Buffer overflow in NTPsec's Zyfer refclock allows local attacker to crash ntpd

CVE-2026-18321 is fixed in ntpsec on 1 platform by DEBIAN-CVE-2026-18321 (version 1.2.5+dfsg-1), released July 31, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-18321
- Priority: Routine
- CVSS: 4.7 (medium)
- EPSS: 0.0011
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 31, 2026

## Description

Buffer overflow in NTPsec's Zyfer refclock allows local attacker to crash ntpd

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | ntpsec Debian 14 | 1.2.5+dfsg-1 | [DEBIAN-CVE-2026-18321](https://patchblox.com/security/data/fix/linux/debian-cve-2026-18321.md) | Jul 31, 2026 |

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Data as of 2026-11-09T07:25:28Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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