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CVE-2021-35210

Cross site scripting in the system log

6.1 MediumFix available

Contao 4.5.x through 4.9.x before 4.9.16, and 4.10.x through 4.11.x before 4.11.5, allows XSS. It is possible to inject code into the tl_log table that will be executed in the browser when the system log is called in the back end.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
None

Exploit likelihood

0.74%Up 0.1 points since Jun 23, 2021
90%50%10%1%

What each source reports

NVD Score used 6.1

Contao 4.5.x through 4.9.x before 4.9.16, and 4.10.x through 4.11.x before 4.11.5, allows XSS. It is possible to inject code into the tl_log table that will be executed in the browser when the system log is called in the back end.

Record
CVE-2021-35210
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS 2.0
4.3 MediumAV:N/AC:M/Au:N/C:N/I:P/A:N
Weakness
CWE-79
Updated
2026-11-02
CVE List No score

Contao 4.5.x through 4.9.x before 4.9.16, and 4.10.x through 4.11.x before 4.11.5, allows XSS. It is possible to inject code into the tl_log table that will be executed in the browser when the system log is called in the back end.

Record
CVE-2021-35210
Updated
2026-11-02
EUVDEUVD-2021-1472 No score

Contao 4.5.x through 4.9.x before 4.9.16, and 4.10.x through 4.11.x before 4.11.5, allows XSS. It is possible to inject code into the tl_log table that will be executed in the browser when the system log is called in the back end.

Record
EUVD-2021-1472
Updated
2026-11-03
GitHub AdvisoriesGHSA-h58v-c6rf-g9f7 6.1

Cross site scripting in the system log

Impact

It is possible to inject code into the tl_log table that will be executed in the browser when the system log is called in the back end.

Patches

Update to Contao 4.9.16 or 4.11.5.

Workarounds

Disable the system log module in the back end for all users (especially admin users).

References

https://contao.org/en/security-advisories/cross-site-scripting-in-the-system-log-2021

For more information

If you have any questions or comments about this advisory, open an issue in contao/contao.

Record
GHSA-h58v-c6rf-g9f7
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness
CWE-79
Updated
2026-11-02
OSV 6.1

Contao 4.5.x through 4.9.x before 4.9.16, and 4.10.x through 4.11.x before 4.11.5, allows XSS. It is possible to inject code into the tl_log table that will be executed in the browser when the system log is called in the back end.

Record
CVE-2021-35210
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Updated
2026-11-02
OSVGHSA-h58v-c6rf-g9f7 6.1

Cross site scripting in the system log

Impact

It is possible to inject code into the tl_log table that will be executed in the browser when the system log is called in the back end.

Patches

Update to Contao 4.9.16 or 4.11.5.

Workarounds

Disable the system log module in the back end for all users (especially admin users).

References

https://contao.org/en/security-advisories/cross-site-scripting-in-the-system-log-2021

For more information

If you have any questions or comments about this advisory, open an issue in contao/contao.

Record
GHSA-h58v-c6rf-g9f7
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness
CWE-79
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
contao/core-bundle
Packagist
 4.5.0 up to 4.9.16
4.9.16
contao/core-bundle
Packagist
 4.10.0 up to 4.11.5
4.11.5
contao/contao
Packagist
 4.5.0 up to 4.9.16
4.9.16
contao/contao
Packagist
 4.10.0 up to 4.11.5
4.11.5
contao/core-bundle
Packagist
 4.5.0 up to 4.9.16, plus listed versions
4.5.14.5.104.5.114.5.124.5.13
Show 45 moreShow less
4.5.144.5.24.5.34.5.44.5.54.5.64.5.74.5.84.5.94.6.04.6.0-RC14.6.0-RC24.6.0-RC34.6.14.6.104.6.114.6.124.6.134.6.144.6.24.6.34.6.44.6.54.6.64.6.74.6.84.6.94.7.04.7.0-RC14.7.0-RC24.7.0-RC34.7.0-RC44.7.14.7.24.7.34.7.44.7.54.7.64.7.74.8.04.8.0-RC14.8.0-RC24.8.14.8.24.8.3
4.9.16
contao/core-bundle
Packagist
 4.10.0 up to 4.11.5, plus listed versions
4.10.14.10.24.10.34.10.44.10.5
Show 9 moreShow less
4.10.64.10.74.11.04.11.0-RC14.11.0-RC24.11.14.11.24.11.34.11.4
4.11.5
contao/contao
Packagist
 4.5.0 up to 4.9.16, plus listed versions
4.5.134.5.144.6.04.6.14.6.10
Show 45 moreShow less
4.6.114.6.124.6.134.6.144.6.24.6.34.6.44.6.54.6.64.6.74.6.84.6.94.7.04.7.0-RC14.7.0-RC24.7.0-RC34.7.0-RC44.7.14.7.24.7.34.7.44.7.54.7.64.7.74.8.04.8.0-RC14.8.0-RC24.8.14.8.24.8.34.8.44.8.54.8.64.8.74.8.84.9.04.9.0-RC14.9.0-RC24.9.14.9.104.9.114.9.124.9.134.9.144.9.15
4.9.16
contao/contao
Packagist
 4.10.0 up to 4.11.5, plus listed versions
4.10.14.10.24.10.34.10.44.10.5
Show 9 moreShow less
4.10.64.10.74.11.04.11.0-RC14.11.0-RC24.11.14.11.24.11.34.11.4
4.11.5

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-35210 is a medium vulnerability (CVSS 6.1) in Contao, published June 23, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.74%, the 54th percentile. Fixed in contao/core-bundle 4.9.16.

References

This page doesn't list everything

Left out here: 31 versions. The JSON record has them.

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