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CVE-2026-121506VulnerabilityPublished

NTS client extension field parsing (extens_client_recv) · Out-of-bounds Read and Write

Affects ntpsecSource GCVE Database

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Authoritative record:CVE-2026-121506· High 7.4

Not known to be exploited · CVSS 7.4 High : upgrade to 1.2.5 soon.

Data as of 3 Nov 2026, 16:14 UTC

CVSS 3.1 base score
7.4High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (GitLab)CVSS 3.17.4
Affects
NTPsec before 1.2.5
Patch
Available – fixed in 1.2.5
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 3 Nov 2026.

What to do

Upgrade ntpsec/ntpsec to 1.2.5.

Affected software

ProductAffectedFixed in
GitHubntpsec/ntpsecpkg:github/ntpsec/ntpsecOther threatsAffected
  • <1.2.5
Fixed in
  • 1.2.5

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in NTPsec version 1.2.5. Users should upgrade to version 1.2.5 or later to remediate this vulnerability. No other mitigation or temporary workaround is indicated.

Description

NTPsec versions before 1.2.5 contain an out-of-bounds read and write vulnerability in the NTS client extension field parsing function (extens_client_recv). This flaw allows a remote attacker who can send NTP server-mode replies to corrupt heap memory and crash the ntpd process. Additionally, when combined with a previously fixed out-of-bounds read in NTS-KE client (fixed in 1.2.4), it can bypass NTS authentication and manipulate the client's time settings.

References

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