CVE-2021-22212

Peer impersonation via truncated symmetric keys

Published Jun 8, 2021 · Updated Aug 3, 2024

Weak key generation in NTPsec 1.2.0 allows attackers to brute-force truncated symmetric keys and impersonate NTP peers. ntpkeygen permits a number-sign byte in generated key text, while ntpd treats that byte as a comment delimiter and pads, truncates, or rejects the resulting key. Exploitation requires an administrator to generate and deploy an affected key, after which man-in-the-middle attackers can break a severely shortened key and impersonate a client or server.

CVSS severity4.0
Medium
EPSS probability0.52%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Weak key generation in NTPsec 1.2.0 allows attackers to brute-force truncated symmetric keys and impersonate NTP peers. ntpkeygen permits a number-sign byte in generated key text, while ntpd treats that byte as a comment delimiter and pads, truncates, or rejects the resulting key. Exploitation requires an administrator to generate and deploy an affected key, after which man-in-the-middle attackers can break a severely shortened key and impersonate a client or server.

The record

CVE
CVE-2021-22212
Published
Jun 8, 2021
Updated
Aug 3, 2024
Vendor
NTPsec
Product
NTPsec
Classifications
CWE-327, T1557
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Jun 8, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion==1.2.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

NTPsec · NTPsecversion==1.2.0

Published CVSS scores

7.4NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:N
4.0GitLab Inc.CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-327Use of a Broken or Risky Cryptographic Algorithm
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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