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Fencer Vulns
medium 4.0

CVE-2021-22212 json

ntpkeygen can generate keys that ntpd fails to parse.

published 2021-06-08 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-9358

cvss
4.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 44%
public exploits
0
none known

Summary

ntpkeygen can generate keys that ntpd fails to parse. NTPsec 1.2.0 allows ntpkeygen to generate keys with '#' characters. ntpd then either pads, shortens the key, or fails to load these keys entirely, depending on the key type and the placement of the '#'. This results in the administrator not being able to use the keys as expected or the keys are shorter than expected and easier to brute-force, possibly resulting in MITM attacks between ntp clients and ntp servers. For short AES128 keys, ntpd generates a warning that it is padding them.

Patch / fix

  • ntpsec Debian 14, Debian 13, Debian 12 1.2.0+dfsg1-4

debian advisories DEBIAN-CVE-2021-22212

  • ntpsec openSUSE Tumbleweed 1.2.1-1.2

opensuse advisories openSUSE-SU-2024:11103-1

  • ntpsec Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 1.2.1-r0

alpine advisories ALPINE-CVE-2021-22212

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-2021-22212 updated cvss 4.0

ntpsec: ntpkeygen can generate keys that ntpd fails to parse

  • 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

Exploit prediction

0.52% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.0 CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:U/C:N/I:H/A:N
NVD 3.1 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
NVD 2.0 5.8 AV:N/AC:M/Au:N/C:P/I:P/A:N

Affected products

  • NTPsec ntpsec

Classification

Weakness
  • CWE-327 Use of a Broken or Risky Cryptographic Algorithm

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.