TI-2026-36452 Aliases CVE-2026-49256

Discourse: Hidden tag names leaked via category serializers

LOW 29CWE-200Published 2026-07-09 · Updated 2026-07-10

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: Present
Impact type: Information disclosure
Confidentiality · integrity · availability: Low · None · None
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-200.

Summary

Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, restricted tag and tag-group names attached to publicly readable categories as allowed_tags, allowed_tag_groups, or required tag groups could leak to anonymous and unauthorized users through category and group endpoints. 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 0.00508 43rd 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: Partial

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

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
discourse	discourse	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	2026.1.5, 2026.4.2, 2026.5.1	Patch available	CNA

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

CPE	Versions	Role	Vendor
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 2026.5.1	Vulnerable	discourse
cpe:2.3:a:discourse:discourse:2026.6.0::::latest:::	2026.6.0	Vulnerable	discourse

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

2026-10-02 Threatist record created from CVE-2026-49256

References

Patch 1

https://github.com/discourse/discourse/releases/tag/v2026.1.5

Advisory 1

https://github.com/discourse/discourse/security/advisories/GHSA-mwp7-572g-6qpx

Other 3

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

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