CVE-2021-21384Public exploit

Command execution via unstripped null bytes

Published Mar 18, 2021 · Updated Aug 3, 2024

Argument injection in Eric Cornelissen's Shescape before 1.1.3 allows attackers to execute shell commands through null-byte payloads. The Unix and Windows escapeShellArg implementations quote shell delimiters without first removing embedded null bytes, letting a shell reinterpret attacker-controlled separators. Exploitation requires a consuming application to pass attacker-controlled input through Shescape and then execute the resulting shell command.

CVSS severity7.8
High
EPSS probability0.58%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Argument injection in Eric Cornelissen's Shescape before 1.1.3 allows attackers to execute shell commands through null-byte payloads. The Unix and Windows escapeShellArg implementations quote shell delimiters without first removing embedded null bytes, letting a shell reinterpret attacker-controlled separators. Exploitation requires a consuming application to pass attacker-controlled input through Shescape and then execute the resulting shell command.

The record

CVE
CVE-2021-21384
Published
Mar 18, 2021
Updated
Aug 3, 2024
Vendor
Eric Cornelissen
Product
Shescape
Classifications
CWE-88, T1059
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 18, 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=< 1.1.3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Eric Cornelissen · Shescapeversion=< 1.1.3

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.3GitHub, Inc.CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:N
4.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-88Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
T1059Command and Scripting Interpreter

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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