CVE-2021-23824Public exploitNetwork attack vector

Cross-site scripting via incomplete attribute escaping

Published Jan 13, 2022 · Updated Sep 16, 2024

Cross-site scripting in Crow before 0.3+4 allows remote attackers to inject executable HTML attributes through unquoted template values. Crow's Mustache escape function omits backtick and equals characters, so an unquoted substitution can introduce an event-handler attribute. Exploitation requires an application to render attacker-controlled data in an unquoted attribute; injected script runs in a visitor's browser, and stored input persists across visits.

CVSS severity6.1
Medium
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Crow before 0.3+4 allows remote attackers to inject executable HTML attributes through unquoted template values. Crow's Mustache escape function omits backtick and equals characters, so an unquoted substitution can introduce an event-handler attribute. Exploitation requires an application to render attacker-controlled data in an unquoted attribute; injected script runs in a visitor's browser, and stored input persists across visits.

The record

CVE
CVE-2021-23824
Published
Jan 13, 2022
Updated
Sep 16, 2024
Vendor
CrowCpp
Product
Crow
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 13, 2022CVE 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 <0.3+4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

CrowCpp · Crowversion=unspecified <0.3+4

Published CVSS scores

6.5SnykCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

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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