CVE-2021-4000Network attack vector

Unauthenticated open redirect via unsafe login URL

Published Dec 3, 2021 · Updated Aug 3, 2024

Open redirect in ShowDoc before 2.9.13 allows remote attackers to send users to untrusted sites via crafted login redirect URLs. Login.vue decodes the redirect query value but previously failed to reject protocol-relative URLs beginning with //, allowing navigation to an attacker-controlled host. No authentication is required; exploitation depends on persuading a user to follow the crafted link, and the demonstrated impact is redirection with limited confidentiality and integrity effects rather than service interruption.

CVSS severity6.5
Medium
EPSS probability0.82%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Open redirect in ShowDoc before 2.9.13 allows remote attackers to send users to untrusted sites via crafted login redirect URLs. Login.vue decodes the redirect query value but previously failed to reject protocol-relative URLs beginning with //, allowing navigation to an attacker-controlled host. No authentication is required; exploitation depends on persuading a user to follow the crafted link, and the demonstrated impact is redirection with limited confidentiality and integrity effects rather than service interruption.

The record

CVE
CVE-2021-4000
Published
Dec 3, 2021
Updated
Aug 3, 2024
Vendor
ShowDoc
Product
ShowDoc
Classifications
CWE-601
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 3, 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 <2.9.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ShowDoc · ShowDocversion=unspecified <2.9.13

Published CVSS scores

6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
6.5huntr.devCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
5.8NVDAV:N/AC:M/Au:N/C:P/I:P/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-601URL Redirection to Untrusted Site ('Open Redirect')

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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