CVE-2021-24031

Exp

In the Zstandard command-line utility prior to v1.4.1, output files were created with default permissions. Correct file permissions (matching the input) would only be set at completion time. Output files could therefore be readable or writable to unintended parties.

Published: 2021-03-04 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-24031 is rated Exploit Available (50/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.06%). 2 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-24031

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-24031

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-07-13 0.05% 0.06% +0.02%
2 2024-12-17 0.07% 0.05% -0.02%
3 2023-03-07 — 0.07% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-24031

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/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: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: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.
 1.8 3.6 [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]

Weakness enumeration for CVE-2021-24031

OS Trackers for CVE-2021-24031

vendor priority summary link
alpine medium CVE-2021-24031: 1 source package rows (zstd); 12 state rows across 7 repos (3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 7, open 5. https://security.alpinelinux.org/vuln/CVE-2021-24031
debian not yet assigned CVE-2021-24031 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-2021-24031
redhat low — https://access.redhat.com/security/cve/CVE-2021-24031
suse medium CVE-2021-24031 severity moderate: SUSE including 336 source package names (0.1.0:libzstd1-1.4.4-1.6.1, 0.1.75:libzstd1-1.4.4-1.6.1, …), 416 product×package rows across 153 product lines (Container bci/bci-init, Container bci/bci-minimal, … (153 product lines)): Fixed 281, Known Affected 135. https://www.suse.com/security/cve/CVE-2021-24031/
ubuntu medium CVE-2021-24031 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): not-affected 9, released 5, DNE 1. https://ubuntu.com/security/CVE-2021-24031

Affected software / configurations for CVE-2021-24031

Vendor Product Version Raw CPE
facebook zstandard < 1.4.1 cpe:2.3:a:facebook:zstandard:*:*:*:*:*:*:*:*

References for CVE-2021-24031

URL Tags
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=981404 Exploit Issue Tracking Mailing List Third Party Advisory
https://github.com/facebook/zstd/issues/1630 Exploit Issue Tracking Third Party Advisory
https://www.facebook.com/security/advisories/cve-2021-24031 Vendor Advisory
cvelogic Threat Intelligence