CVE-2026-33393 (GCVE-0-2026-33393)
Vulnerability from cvelistv5 – Published: 2026-03-19 22:04 – Updated: 2026-03-20 20:15
VLAI
EPSS
VEX
Title
Discourse fixes loose hostname matching in spam host allowlist
Summary
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the `allowed_spam_host_domains` check used `String#end_with?` without domain boundary validation, allowing domains like `attacker-example.com` to bypass spam protection when `example.com` was allowlisted. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 require exact match or proper subdomain match (preceded by `.`) to prevent suffix-based bypass of `newuser_spam_host_threshold`. No known workarounds are available.
Severity
4.3 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-03-20 20:15 UTC
CWE
- CWE-284 - Improper Access Control
Assigner
GitHub_M
CNA
References
4 references
| URL | Tags |
|---|---|
| https://github.com/discourse/discourse/security/a… | x_refsource_CONFIRM |
| https://github.com/discourse/discourse/commit/80b… | x_refsource_MISC |
| https://github.com/discourse/discourse/commit/d84… | x_refsource_MISC |
| https://github.com/discourse/discourse/commit/f99… | x_refsource_MISC |
Impacted products
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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