Home/CVE/Contao >=4.0.0 allows backend XSS via HTML attributes to an HTML field. Fixed in 4.4.56, 4.9.18, 4.11.7.
CVE

CVE-2021-35955

Contao >=4.0.0 allows backend XSS via HTML attributes to an HTML field. Fixed in 4.4.56, 4.9.18, 4.11.7.

Contao >=4.0.0 allows backend XSS via HTML attributes to an HTML field. Fixed in 4.4.56, 4.9.18, 4.11.7.

MEDIUM · CVSS 4.8 EPSS 0.00364
Monitor
  • No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
▤

Affected Products & Versions

3
contao>= 4.0.0 and < 4.4.56
contao>= 4.5.0 and < 4.9.18
contao>= 4.10.0 and < 4.11.7
▤

Affected Packages

2
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
Packagist contao/contao MEDIUM fixed in 4.4.56
Packagist contao/core-bundle MEDIUM fixed in 4.4.56
▣

Scoring & Timeline

4.8
MEDIUM · CVSS v3.1 · cve@mitre.org
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD12 Aug 2021 · 03:15 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
🔗

References & Sources

2
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://contao.org/en/news/contao-4-9-16-and-4-11-5-are-available.htmlVendor Advisory
https://github.com/contao/contao/security/advisories/GHSA-hr3h-x6gq-rqcpThird Party Advisory
Intelligence Graph · click any node to traverse
CVETechnique ActorTool Family
drag to reposition · click any node to traverse · button top-right enlarges
External lookups - second-class, for what we don’t hold ourselves
NVDCVE.orgCISAVulnersExploit-DBGitHub PoCVulnCheck KEVGreyNoise
Vulnerabilities
CISA KEV catalog
CWE weaknesses
CAPEC attack patterns
Package vulnerabilities
Threat intelligence
Threat actors
Tools & malware
ATT&CK techniques
IOCs
Detection & defense
Sigma rules
YARA rules
Atomic Red Team tests
D3FEND countermeasures
Compliance
NIST 800-53
ISO 27001:2022
SOC 2 TSC
PCI-DSS v4.0
CIS Controls v8.1
About
All capabilities
Live statistics
Data sources
Privacy policy
Terms of service
threatengine.sh  ·  Open-source threat intelligence platform  ·  100+ authoritative sources  ·  Every fact traces to its origin