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CVE-2026-121506

Out-of-bounds Write in NTPsec

7.4 HighFix available

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

0.45%Unchanged since Nov 4, 2026
90%50%10%1%

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 HighCVSS: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 HighCVSS: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 HighCVSS: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 HighCVSS: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 HighCVSS: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 HighCVSS: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 HighCVSS: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

Affected packages
PackageAffectedFixed
ntpsec
Debian: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 less
1.2.3+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
ntpsec
Debian:13
All versions, plus listed versions
1.2.3+dfsg1-81.2.4+dfsg-11.2.5+dfsg-1
None known
ntpsec
Debian:14
before 1.2.5+dfsg-1, plus listed versions
1.2.3+dfsg1-81.2.4+dfsg-1
1.2.5+dfsg-1
ntpsec
Ubuntu: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
ntpsec
Ubuntu: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
ntpsec
Ubuntu: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
ntpsec
Ubuntu: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
ntpsec
Ubuntu:26.10
All versions, plus listed versions
1.2.3+dfsg1-8ubuntu21.2.3+dfsg1-8ubuntu3
None known
ntpsec
Ubuntu:26.04:LTS
All versions, plus listed versions
1.2.3+dfsg1-8ubuntu11.2.3+dfsg1-8ubuntu2
None known

History

History
RecordedChangedSources
affected, aliases, facts, referencesOSV
affected, aliases, referencesOSV
referencesOSV
publishedEUVD, NVD
publishedEUVD
factsCVE List, EUVD
aliases, cwes, references, severity, titleCVE List, GitHub Advisories
first indexedEUVD

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

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