CVE-2021-23422

Code execution via unguarded inline tag commands

Published Aug 16, 2021 · Updated Sep 16, 2024

OS command injection in Bikeshed before 3.0.0 allows attackers to execute commands by supplying a crafted source document. The inline-tag processor accepts Inline Tag Command metadata and reaches subprocess.Popen without requiring explicit execution authorization. Exploitation requires a user or automated build to process the untrusted document; commands run with that process's privileges, and their output is embedded in generated HTML.

CVSS severity7.8
High
EPSS probability0.79%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OS command injection in Bikeshed before 3.0.0 allows attackers to execute commands by supplying a crafted source document. The inline-tag processor accepts Inline Tag Command metadata and reaches subprocess.Popen without requiring explicit execution authorization. Exploitation requires a user or automated build to process the untrusted document; commands run with that process's privileges, and their output is embedded in generated HTML.

The record

CVE
CVE-2021-23422
Published
Aug 16, 2021
Updated
Sep 16, 2024
Vendor
Bikeshed Project
Product
Bikeshed
Classifications
CWE-78, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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 <3.0.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Bikeshed Project · Bikeshedversion=unspecified <3.0.0

Published CVSS scores

7.8SnykCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
7.8National Vulnerability DatabaseCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8National Vulnerability DatabaseAV:N/AC:M/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
T1204.002User Execution: Malicious File

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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