CVE-2021-24032 [Medium] | Security Vulnerability in Zstandard

Beginning in v1.4.1 and prior to v1.4.9, due to an incomplete fix for CVE-2021-24031, the Zstandard command-line utility created output files with default permissions and restricted those permissions immediately afterwards. Output files could therefore momentarily be readable or writable to unintended parties.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.02%	0.35%	+0.33%
2	2026-02-02	0.06%	0.02%	-0.04%
3	2026-01-11	—	0.06%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.02%

0.35%

+0.33%

2026-02-02

0.06%

0.02%

-0.04%

2026-01-11

—

0.06%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
4.7	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/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:H) Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work. 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:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:N) Service keeps running; no real outage angle.	1.0	3.6	[email protected]
1.9	2.0	LOW	`AV:L/AC:M/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:M) Exploitation needs some favorable conditions, but not exceptional ones. 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.	3.4	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

4.7

3.1

MEDIUM

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/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:H): Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
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:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:N): Service keeps running; no real outage angle.

1.0

3.6

[email protected]

1.9

2.0

LOW

AV:L/AC:M/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:M): Exploitation needs some favorable conditions, but not exceptional ones.
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.

3.4

2.9

[email protected]

OS Trackers for CVE-2021-24032

vendor	priority	summary	link
`alpine`	medium	CVE-2021-24032: 1 source package rows (zstd); 14 state rows across 9 repos (3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 9, open 5.	https://security.alpinelinux.org/vuln/CVE-2021-24032
`debian`	not yet assigned	CVE-2021-24032 not yet assigned priority: Debian including 1 source packages (libzstd), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2021-24032
`redhat`	low	—	https://access.redhat.com/security/cve/CVE-2021-24032
`suse`	medium	CVE-2021-24032 severity moderate: SUSE including 105 source package names (0.1.0:libzstd1-1.4.4-1.6.1, 0.1.75:libzstd1-1.4.4-1.6.1, …), 185 product×package rows across 152 product lines (Container bci/bci-init, Container bci/bci-minimal, … (152 product lines)): Fixed 185.	https://www.suse.com/security/cve/CVE-2021-24032/
`ubuntu`	medium	CVE-2021-24032 medium priority: Ubuntu including 1 source packages (libzstd), 15 status rows across 15 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, trusty, upstream, xenial): released 14, DNE 1.	https://ubuntu.com/security/CVE-2021-24032

Affected software / configurations for CVE-2021-24032

Vendor	Product	Version	Raw CPE
facebook	zstandard	>= 1.4.1, < 1.4.9	cpe:2.3:a:facebook:zstandard::::::::

References for CVE-2021-24032

URL	Tags
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982519	Patch Third Party Advisory
https://github.com/facebook/zstd/issues/2491	Issue Tracking Patch Third Party Advisory
https://www.facebook.com/security/advisories/cve-2021-24032	Third Party Advisory

URL

CVE-2021-24032

Exploit prediction scoring system (EPSS) score for CVE-2021-24032

Common vulnerability scoring system (CVSS) metrics for CVE-2021-24032

Weakness enumeration for CVE-2021-24032

OS Trackers for CVE-2021-24032

Affected software / configurations for CVE-2021-24032

References for CVE-2021-24032