GitHub Advisory DatabaseGHSA-HR3H-X6GQ-RQCPCross site scripting via HTML attributes in the back end
3.5 Low
CVSS2
Attack Vector
NETWORK
Attack Complexity
MEDIUM
Authentication
SINGLE
Confidentiality Impact
NONE
Integrity Impact
PARTIAL
Availability Impact
NONE
AV:N/AC:M/Au:S/C:N/I:P/A:N
4.8 Medium
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
0.001 Low
EPSS
Percentile
22.7%
Impact
It is possible for untrusted users to inject malicious code into HTML attributes in the back end, which will be executed both in the element preview (back end) and on the website (front end).
Installations are only affected if there are untrusted back end users who have the rights to modify HTML fields (e.g. TinyMCE).
Patches
Update to Contao 4.4.56, 4.9.18 or 4.11.7
Workarounds
Disable all fields that allow HTML for untrusted back end users or disable the login for these users.
References
https://contao.org/en/security-advisories/cross-site-scripting-via-html-attributes-in-the-back-end
For more information
If you have any questions or comments about this advisory, open an issue in contao/contao.
Credits
Thanks to Mikhail Khramenkov and Moritz Vondano for reporting this security issue.
Affected configurations
| CPE | Name | Operator | Version |
|---|---|---|---|
| contao/core-bundle | lt | 4.11.7 | |
| contao/core-bundle | lt | 4.9.18 | |
| contao/contao | lt | 4.11.7 | |
| contao/contao | lt | 4.9.18 | |
| contao/contao | lt | 4.4.56 | |
| contao/core-bundle | lt | 4.4.56 |
References
contao.org/en/news/contao-4-9-16-and-4-11-5-are-available.html
contao.org/en/security-advisories/cross-site-scripting-via-html-attributes-in-the-back-end.html
github.com/advisories/GHSA-hr3h-x6gq-rqcp
github.com/contao/contao/security/advisories/GHSA-hr3h-x6gq-rqcp
github.com/FriendsOfPHP/security-advisories/blob/master/contao/contao/CVE-2021-35955.yaml
github.com/FriendsOfPHP/security-advisories/blob/master/contao/core-bundle/CVE-2021-35955.yaml
nvd.nist.gov/vuln/detail/CVE-2021-35955
Related
3.5 Low
CVSS2
Attack Vector
NETWORK
Attack Complexity
MEDIUM
Authentication
SINGLE
Confidentiality Impact
NONE
Integrity Impact
PARTIAL
Availability Impact
NONE
AV:N/AC:M/Au:S/C:N/I:P/A:N
4.8 Medium
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
0.001 Low
EPSS
Percentile
22.7%