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TI-2026-39992 Aliases CVE-2026-55424

Discourse: Topic featured link susceptible to stored XSS

Priority LOW 35CWE-79Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
Passive
Attack complexity
Low
Attack requirements
Present
Impact type
Cross-site scripting
Confidentiality · integrity · availability
High · High · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-79.

Summary

Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, a topic "featured link" was not sufficiently normalized and escaped before being rendered in the topic list, allowing a user who can set a featured link to inject JavaScript when default Content Security Policy protections were modified or disabled. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00415 36th percentileScored 2026-11-07
Fix Fixed discourse (discourse): 2026.1.5, 2026.4.2, 2026.5.1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
discoursediscourse2026.1.0-latest to before 2026.1.5; 2026.4.0-latest to before 2026.4.2; 2026.5.0-latest to before 2026.5.12026.1.5, 2026.4.2, 2026.5.1Patch availableCNA
  • discourse Vendordiscourse Affected 2026.1.0-latest to before 2026.1.5; 2026.4.0-latest to before 2026.4.2; 2026.5.0-latest to before 2026.5.1 Fixed in 2026.1.5, 2026.4.2, 2026.5.1 Patch available CNA

CPE configurations NVD · 2

CPEVersionsRoleVendor
cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*2026.1.0 to before 2026.1.5; 2026.4.0 to before 2026.4.2; 2026.5.0 to before 2026.5.1Vulnerablediscourse
cpe:2.3:a:discourse:discourse:2026.6.0:*:*:*:latest:*:*:*2026.6.0Vulnerablediscourse
  • cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:* Versions 2026.1.0 to before 2026.1.5; 2026.4.0 to before 2026.4.2; 2026.5.0 to before 2026.5.1 Vulnerable ·discourse
  • cpe:2.3:a:discourse:discourse:2026.6.0:*:*:*:latest:*:*:* Versions 2026.6.0 Vulnerable ·discourse

Remediation

  • Fix · CNA discourse (discourse) Fixed in 2026.1.5, 2026.4.2, 2026.5.1

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-55424

References

Patch 4

Advisory 1

Other 4

  • TI-2021-19656 Denial of Service in discourse CVSS 3.1MEDIUM 6.8
  • TI-2024-36150 Potential Backup file leaked via Nginx in Discourse CVSS 3.1HIGH 7.5
  • TI-2021-18002 RCE via malicious SNS subscription payload CVSS 3.1CRITICAL 10.0
  • TI-2026-24651 Discourse: Open redirect via `sso_destination_url` cookie in `enter` CVSS 4.0MEDIUM 5.1
  • TI-2026-22278 Discourse leaks private topic title and post excerpt via user action API endpoint CVSS 4.0HIGH 8.7
  • TI-2023-24152 Unauthenticated access to new private chat messages in Discourse CVSS 3.1HIGH 7.5
See all 262 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences