CVE-2021-24031Public exploit

Local file disclosure via delayed permission restriction

Published Mar 4, 2021 · Updated Aug 3, 2024

Incorrect file permissions in the Zstandard command-line utility before 1.4.1 allow local users to read output file contents. The file-output path opens each destination with process-default permissions and applies the source file's restrictive mode only after processing completes. A local user with access to the destination path can read data while a large output file remains open.

CVSS severity5.5
Medium
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect file permissions in the Zstandard command-line utility before 1.4.1 allow local users to read output file contents. The file-output path opens each destination with process-default permissions and applies the source file's restrictive mode only after processing completes. A local user with access to the destination path can read data while a large output file remains open.

The record

CVE
CVE-2021-24031
Published
Mar 4, 2021
Updated
Aug 3, 2024
Vendor
Meta Platforms, Inc.
Product
Zstandard
Classifications
CWE-277, CWE-276, T1005
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 4, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <1.4.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Meta Platforms, Inc. · Zstandardversion=unspecified <1.4.1

Published CVSS scores

5.5NISTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
2.1NISTAV:L/AC:L/Au:N/C:P/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-277Insecure Inherited Permissions
CWE-276Incorrect Default Permissions
T1005Data from Local System

Public exploit references

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Technologies

Your stack

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Your stack

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