CVE-2021-3571 [High] | Memory Corruption in Linuxptp

A flaw was found in the ptp4l program of the linuxptp package. When ptp4l is operating on a little-endian architecture as a PTP transparent clock, a remote attacker could send a crafted one-step sync message to cause an information leak or crash. The highest threat from this vulnerability is to data confidentiality and system availability. This flaw affects linuxptp versions before 3.1.1 and before 2.0.1.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2025-11-21	0.43%	0.72%	+0.29%
2	2025-11-18	0.72%	0.43%	-0.29%
3	2025-10-08	—	0.72%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2025-11-21

0.43%

0.72%

+0.29%

2025-11-18

0.72%

0.43%

-0.29%

2025-10-08

—

0.72%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.1	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:L) Some sensitive info could get out, but not a total data dump. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	2.8	4.2	[email protected]
5.5	2.0	MEDIUM	`AV:N/AC:L/Au:S/C:P/I:N/A:P` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:S) A single authentication is required. Confidentiality impact (C:P) Partial confidentiality impact. Integrity impact (I:N) No integrity impact. Availability impact (A:P) Partial availability impact.	8.0	4.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.1

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L): Some sensitive info could get out, but not a total data dump.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

2.8

4.2

[email protected]

5.5

2.0

MEDIUM

AV:N/AC:L/Au:S/C:P/I:N/A:P Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:S): A single authentication is required.
Confidentiality impact (C:P): Partial confidentiality impact.
Integrity impact (I:N): No integrity impact.
Availability impact (A:P): Partial availability impact.

8.0

4.9

[email protected]

OS Trackers for CVE-2021-3571

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2021-3571 not yet assigned priority: Debian including 1 source packages (linuxptp), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2021-3571
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2021-3571
`suse`	high	CVE-2021-3571 severity important: SUSE including 2 source package names (linuxptp, linuxptp-3.1.1-1.el8), 45 product×package rows across 45 product lines (HPE Helion OpenStack 8, SUSE CaaS Platform 4.0, … (45 product lines)): Known Not Affected 44, Fixed 1.	https://www.suse.com/security/cve/CVE-2021-3571/
`ubuntu`	medium	CVE-2021-3571 medium priority: Ubuntu including 1 source packages (linuxptp), 11 status rows across 11 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, trusty, upstream, xenial): not-affected 7, ignored 2, DNE 1, released 1.	https://ubuntu.com/security/CVE-2021-3571

Affected software / configurations for CVE-2021-3571

Vendor	Product	Version	Raw CPE
linuxptp_project	linuxptp	< 2.0.1	cpe:2.3:a:linuxptp_project:linuxptp::::::::
linuxptp_project	linuxptp	>= 3.0, < 3.1.1	cpe:2.3:a:linuxptp_project:linuxptp::::::::
redhat	enterprise_linux	8.0	cpe:2.3:o:redhat:enterprise_linux:8.0::::-:::
fedoraproject	fedora	33	cpe:2.3:o:fedoraproject:fedora:33:::::::*
fedoraproject	fedora	34	cpe:2.3:o:fedoraproject:fedora:34:::::::*

References for CVE-2021-3571

URL	Tags
https://bugzilla.redhat.com/show_bug.cgi?id=1966241	Issue Tracking Patch Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RHRUVSDP673LXJ5HGIPQPWPIYUPWYQA7/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VUBKTRCMJ6VKS7DIBSZQB4ATSKVCJYXJ/

URL

CVE-2021-3571

Exploit prediction scoring system (EPSS) score for CVE-2021-3571

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3571

Weakness enumeration for CVE-2021-3571

OS Trackers for CVE-2021-3571

Affected software / configurations for CVE-2021-3571

References for CVE-2021-3571