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CVE-2026-121506

Out-of-bounds Write in NTPsec

No exploitation reported by the sources we read.

  • Published2026-11-03
  • WeaknessCWE-787

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

An out-of-bounds read and write in NTS client extension field parsing (extens_client_recv) in NTPsec before 1.2.5 allows a remote attacker who can send NTP server-mode replies to an NTS client to corrupt heap memory and crash ntpd, and, combined with the NTS-KE client out-of-bounds read fixed in 1.2.4, to bypass NTS authentication and set the client's time, via an NTS Authenticator and Encrypted Extension Fields field whose nonce length exceeds the field.

Timeline

dates in UTC
  1. 2026-11-0314:17CVE publishedCNA

Observed activity

isMalicious corpus · updated 2026-11-03 15:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-121506?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-121506?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

Products declared by the CNA

As GitLab, the CNA that assigned this CVE, declared them in the CVE record; versions as written. NVD lists no product for this CVE yet: this is the only product data so far.

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-11-03

Neither OSV.dev nor the vendor advisories we read list affected versions for CVE-2026-121506 yet.

Full record on NVD

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

Sources

  • CISA-ADPSSVC decisionnone2026-11-03
  • OpenCVESSVC decisionnone—
  • CNACVSS 3.17.42026-11-03
  • CNAweakness (CWE)CWE-7872026-11-03
  • NVDweakness (CWE)CWE-787read 2026-11-03

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
Published
2026-11-03
Last Modified
2026-11-03
NVD status
Received

Frequently asked questions

What is CVE-2026-121506?

An out-of-bounds read and write in NTS client extension field parsing (extens_client_recv) in NTPsec before 1.2.5 allows a remote attacker who can send NTP server-mode replies to an NTS client to corrupt heap memory and crash ntpd, and, combined with the NTS-KE client out-of-bounds read fixed in 1.2.4, to bypass NTS authentication and set the client's time, via an NTS Authenticator and Encrypted Extension Fields field whose nonce length exceeds the field.

Is CVE-2026-121506 actively exploited?

Active exploitation of CVE-2026-121506 has not been confirmed.

What is the CVSS score for CVE-2026-121506?

CVE-2026-121506 has a CVSS v3 base score of 7.4 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H.

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