CVE-2026-121505

Out-of-bounds Read in NTPsec

3.7 LowFix available

An out-of-bounds read in the NTS-KE client response parser (nts_client_process_response_core) in NTPsec before 1.2.4 allows a malicious NTS-KE server to read the client's stack memory, including pointers that defeat ASLR, which the client then sends in cleartext as NTS cookies, via an NTS-KE record whose declared length exceeds the data received.

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: Low
Integrity: None
Availability: None

Exploit likelihood

0.29%Unchanged since Nov 4, 2026

What each source reports

CVE List Score used 3.7

Out-of-bounds Read in NTPsec

Record: CVE-2026-121505
CVSS 3.1: 3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-125
Updated: 2026-11-03

EUVDEUVD-2026-115826 3.7

Record: EUVD-2026-115826
CVSS 3.1: 3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-03

GitHub AdvisoriesGHSA-rjr3-53fv-wjrf 3.7

An out-of-bounds read in the NTS-KE client response parser (nts_client_process_response_core) in...

Record: GHSA-rjr3-53fv-wjrf
CVSS 3.1: 3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-125
Updated: 2026-11-03

NVD 3.7

Record: CVE-2026-121505
CVSS 3.1: 3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-125
Updated: 2026-11-03

OSV 3.7

Out-of-bounds Read in NTPsec

Record: CVE-2026-121505
CVSS 3.1: 3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-125
Updated: 2026-11-05

OSVDEBIAN-CVE-2026-121505 3.7

Record: DEBIAN-CVE-2026-121505
CVSS 3.1: 3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-06

OSVUBUNTU-CVE-2026-121505 3.7

Record: UBUNTU-CVE-2026-121505
CVSS 3.1: 3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated: 2026-11-05

Affected products

ntpsec

Affected packages

Affected packages
Package	Affected	Fixed
`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 1.2.4+dfsg-1, plus listed versions 1.2.3+dfsg1-8	1.2.4+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
Recorded	Changed	Sources
Nov 6, 2026	affected, aliases, facts, references	OSV
Nov 5, 2026	affected, aliases, references	OSV
Nov 4, 2026	references	CVE List, EUVD, NVD, OSV
Nov 3, 2026	published	EUVD, NVD
Nov 3, 2026	facts, published	EUVD
Nov 3, 2026	aliases, cwes, references, severity, title	CVE List, GitHub Advisories
Nov 3, 2026	first indexed	EUVD

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-121505 is a low vulnerability (CVSS 3.7) in Ntpsec, published November 3, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.29%, the 22nd percentile. Fixed in ntpsec 1.2.4+dfsg-1.

References

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