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Fencer Vulns
medium 4.7

CVE-2026-18321 json

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') in ntpsec

published 2026-07-31 3 mo ago modified 2026-08-28 2 mo ago also EUVD-2026-51593

cvss
4.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits
0
none known

Summary

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

Patch / fix

  • NTPsec ntpsec 1.2.5
  • ntpsec Debian 14 1.2.5+dfsg-1

debian advisories DEBIAN-CVE-2026-18321

  • ntpsec openSUSE Tumbleweed 1.2.5-1.1

opensuse advisories openSUSE-SU-2026:11417-1

  • ntpsec Alpine 3.24 1.2.5-r0

alpine advisories ALPINE-CVE-2026-18321

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-18321 updated cvss 4.7

ntpsec: NTPsec: Denial of Service via buffer overflow in Zyfer refclock

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.11% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.7 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • NTPsec ntpsec

Classification

Weakness
  • CWE-120 Buffer Copy without Checking Size of Input

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.