CVE-2021-3981 [Low] | Security Vulnerability in Grub2

A flaw in grub2 was found where its configuration file, known as grub.cfg, is being created with the wrong permission set allowing non privileged users to read its content. This represents a low severity confidentiality issue, as those users can eventually read any encrypted passwords present in grub.cfg. This flaw affects grub2 2.06 and previous versions. This issue has been fixed in grub upstream but no version with the fix is currently released.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.02%	0.31%	+0.29%
2	2025-11-21	0.06%	0.02%	-0.04%
3	2025-11-18	—	0.06%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.02%

0.31%

+0.29%

2025-11-21

0.06%

0.02%

-0.04%

2025-11-18

—

0.06%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
3.3	3.1	LOW	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. 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:N) Service keeps running; no real outage angle.	1.8	1.4	[email protected]
2.1	2.0	LOW	`AV:L/AC:L/Au:N/C:P/I:N/A:N` Click to expand Access vector (AV:L) Requires local access to the target system. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:P) Partial confidentiality impact. Integrity impact (I:N) No integrity impact. Availability impact (A:N) No availability impact.	3.9	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

3.3

3.1

LOW

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

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
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:N): Service keeps running; no real outage angle.

1.8

1.4

[email protected]

2.1

2.0

LOW

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

Access vector (AV:L): Requires local access to the target system.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:P): Partial confidentiality impact.
Integrity impact (I:N): No integrity impact.
Availability impact (A:N): No availability impact.

3.9

2.9

[email protected]

OS Trackers for CVE-2021-3981

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2021-3981 not yet assigned priority: Debian including 1 source packages (grub2), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 1.	https://security-tracker.debian.org/tracker/CVE-2021-3981
`gentoo`	high	CVE-2021-3981: 1 GLSA(s) (202209-12), 1 atom(s) (sys-boot/grub); latest impact high.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-3981
`redhat`	low	—	https://access.redhat.com/security/cve/CVE-2021-3981
`suse`	medium	CVE-2021-3981 severity moderate: SUSE including 114 source package names (grub, grub2, …), 359 product×package rows across 68 product lines (HPE Helion OpenStack 8, SUSE CaaS Platform 4.0, … (68 product lines)): Known Not Affected 248, Fixed 111.	https://www.suse.com/security/cve/CVE-2021-3981/
`ubuntu`	low	CVE-2021-3981 low priority: Ubuntu including 3 source packages (grub2, grub2-signed, grub2-unsigned), 41 status rows across 15 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 22, needs-triage 8, ignored 6, released 4, DNE 1.	https://ubuntu.com/security/CVE-2021-3981

Affected software / configurations for CVE-2021-3981

Vendor	Product	Version	Raw CPE
gnu	grub2	<= 2.06	cpe:2.3:a:gnu:grub2::::::::
fedoraproject	fedora	34	cpe:2.3:o:fedoraproject:fedora:34:::::::*

References for CVE-2021-3981

URL	Tags
http://www.openwall.com/lists/oss-security/2024/01/15/3
https://bugzilla.redhat.com/show_bug.cgi?id=2024170	Issue Tracking Patch Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AI776L35DDYPCSAAJPJM3ZEQYSFZHBJX/
https://security.gentoo.org/glsa/202209-12	Third Party Advisory

URL

CVE-2021-3981

Exploit prediction scoring system (EPSS) score for CVE-2021-3981

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3981

Weakness enumeration for CVE-2021-3981

OS Trackers for CVE-2021-3981

Affected software / configurations for CVE-2021-3981

References for CVE-2021-3981