CVE-2026-121506
Out-of-bounds Write in NTPsec
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
7.4
Out-of-bounds Write in NTPsec
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.
- Record
CVE-2026-121506- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-03
EUVDEUVD-2026-115827
7.4
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.
- Record
EUVD-2026-115827- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-28fm-m2x6-h5pf
7.4
An out-of-bounds read and write in NTS client extension field parsing (extens_client_recv) in...
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.
- Record
GHSA-28fm-m2x6-h5pf- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-03
NVD
7.4
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.
- Record
CVE-2026-121506- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-03
OSV
7.4
Out-of-bounds Write in NTPsec
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.
- Record
CVE-2026-121506- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-05
OSVDEBIAN-CVE-2026-121506
7.4
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.
- Record
DEBIAN-CVE-2026-121506- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H - Updated
- 2026-11-06
OSVUBUNTU-CVE-2026-121506
7.4
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.
- Record
UBUNTU-CVE-2026-121506- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H - Updated
- 2026-11-05
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
ntpsecDebian:12 |
All versions, plus listed versions 1.2.2+dfsg1-11.2.2+dfsg1-1+deb12u11.2.2+dfsg1-21.2.2+dfsg1-31.2.2+dfsg1-4 Show 10 moreShow less1.2.3+dfsg1-11.2.3+dfsg1-21.2.3+dfsg1-31.2.3+dfsg1-41.2.3+dfsg1-51.2.3+dfsg1-61.2.3+dfsg1-71.2.3+dfsg1-81.2.4+dfsg-11.2.5+dfsg-1 |
None known |
ntpsecDebian:13 |
All versions, plus listed versions 1.2.3+dfsg1-81.2.4+dfsg-11.2.5+dfsg-1 |
None known |
ntpsecDebian:14 |
before 1.2.5+dfsg-1, plus listed versions 1.2.3+dfsg1-81.2.4+dfsg-1 |
1.2.5+dfsg-1 |
ntpsecUbuntu:18.04:LTS |
All versions, plus listed versions 1.0.0+dfsg1-11.0.0+dfsg1-31.1.0+dfsg1-11.1.0+dfsg1-1ubuntu0.11.1.0+dfsg1-1ubuntu0.2 |
None known |
ntpsecUbuntu:20.04:LTS |
All versions, plus listed versions 1.1.3+dfsg1-21.1.7+dfsg1-11.1.7+dfsg1-21.1.8+dfsg1-11.1.8+dfsg1-31.1.8+dfsg1-41.1.8+dfsg1-4build1 |
None known |
ntpsecUbuntu:22.04:LTS |
All versions, plus listed versions 1.2.0+dfsg1-41.2.1+dfsg1-21.2.1+dfsg1-31.2.1+dfsg1-3ubuntu11.2.1+dfsg1-4 |
None known |
ntpsecUbuntu:24.04:LTS |
All versions, plus listed versions 1.2.2+dfsg1-21.2.2+dfsg1-31.2.2+dfsg1-41.2.2+dfsg1-4build11.2.2+dfsg1-4build2 |
None known |
ntpsecUbuntu:26.10 |
All versions, plus listed versions 1.2.3+dfsg1-8ubuntu21.2.3+dfsg1-8ubuntu3 |
None known |
ntpsecUbuntu:26.04:LTS |
All versions, plus listed versions 1.2.3+dfsg1-8ubuntu11.2.3+dfsg1-8ubuntu2 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, aliases, facts, references | OSV | |
| affected, aliases, references | OSV | |
| references | OSV | |
| published | EUVD, NVD | |
| published | EUVD | |
| facts | CVE List, EUVD | |
| aliases, cwes, references, severity, title | CVE List, GitHub Advisories | |
| first indexed | EUVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-121506 is a high vulnerability (CVSS 7.4) in Ntpsec, published November 3, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.45%, the 39th percentile. Fixed in ntpsec 1.2.5+dfsg-1.
References
gitlab.com/NTPsec/ntpsec/-/commit/0a36941e499d533dfbc3fb6b1fcd8c367679d719
gitlab.com/NTPsec/ntpsec/-/work_items/902
nvd.nist.gov/vuln/detail/CVE-2026-121506
github.com/advisories/GHSA-28fm-m2x6-h5pf
github.com/CVEProject/cvelistV5/tree/main/cves/2026/121xxx/CVE-2026-121506.json
gitlab.com/NTPsec/ntpsec
security-tracker.debian.org/tracker/CVE-2026-121506
ubuntu.com/security/CVE-2026-121506
cve.org/CVERecord?id=CVE-2026-121506