CVE-2026-121506
High
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.
SeverityHigh
CVSS7.4
Exploit probability—
ProductNTPsec
PublishedNov 3, 2026
First seenNov 4, 2026
Weakness typeCWE-787Out-of-bounds write
How to fix
Update
- NTPsec NTPsec1.2.5 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| NTPsec NTPsec | 1.1.4 ≤ v < 1.2.5 | 1.2.5 |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.