CVE-2021-21338Network attack vector

Phishing redirects via scheme-relative login URLs

Published Mar 23, 2021 · Updated Aug 3, 2024

Open redirect in TYPO3 CMS Login Handling allows remote attackers to send users of affected releases to arbitrary external sites. GeneralUtility::sanitizeLocalUrl() treats scheme-relative URLs beginning with // as local, allowing a login redirect target to name an external host. No authentication is required, but successful phishing requires a victim to follow a crafted TYPO3 login link and accept the resulting redirect.

CVSS severity4.7
Medium
EPSS probability1.10%
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 TYPO3 CMS Login Handling allows remote attackers to send users of affected releases to arbitrary external sites. GeneralUtility::sanitizeLocalUrl() treats scheme-relative URLs beginning with // as local, allowing a login redirect target to name an external host. No authentication is required, but successful phishing requires a victim to follow a crafted TYPO3 login link and accept the resulting redirect.

The record

CVE
CVE-2021-21338
Published
Mar 23, 2021
Updated
Aug 3, 2024
Vendor
in2code GmbH
Product
TYPO3 CMS
Classifications
CWE-601, CAPEC-178, T1566.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 23, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=>= 10.0.0, <= 10.4.13
  2. Affected versionversion=>= 11.0.0, <= 11.1.0
  3. Affected versionversion=>= 6.2.0, <= 6.2.56
  4. Affected versionversion=>= 7.0.0, <= 7.6.50
  5. Affected versionversion=>= 8.0.0, <= 8.7.39
  6. Affected versionversion=>= 9.0.0, <= 9.5.24

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

in2code GmbH · TYPO3 CMSversion=>= 10.0.0, <= 10.4.13; version=>= 11.0.0, <= 11.1.0; version=>= 6.2.0, <= 6.2.56; version=>= 7.0.0, <= 7.6.50; version=>= 8.0.0, <= 8.7.39; version=>= 9.0.0, <= 9.5.24

Published CVSS scores

4.7GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
5.8NIST NVDAV: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')
CAPEC-178Cross-Site Flashing
T1566.002Phishing: Spearphishing Link

Public exploit references

No public exploit references are available in this record.

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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