CVE-2026-23743
Published: 28 January 2026
Summary
CVE-2026-23743 is a high-severity Exposure of Sensitive Information to an Unauthorized Actor (CWE-200) vulnerability in Discourse Discourse. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 14.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Automated marking applies security attributes to system outputs, making it harder for attackers to exploit unmarked sensitive information leading to unauthorized exposure.
Proper attribute retention and permitted-value enforcement limits unauthorized actors from accessing sensitive information lacking correct labels.
Prevents unauthorized exposure of sensitive information by prohibiting untrusted external systems from processing or storing it.
By enforcing authorization matching prior to sharing, the control reduces the risk of exposing sensitive information to unauthorized actors.
Review and removal of nonpublic information from publicly accessible systems directly prevents exposure of sensitive data to unauthorized actors.
Data mining protection mechanisms detect and block unauthorized bulk extraction of sensitive data, directly mitigating exposure to unauthorized actors.
Literacy training teaches users to recognize and avoid actions that result in unauthorized exposure of sensitive information.
Retaining and monitoring training records confirms personnel have completed privacy and security awareness training on handling sensitive data, reducing the chance of unauthorized exposure due to lack of knowledge.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Direct exploitation of public-facing Discourse web app via crafted permalink requests to leak restricted resource metadata (titles, slugs).
NVD Description
Discourse is an open source discussion platform. In versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0, permalinks pointing to access-restricted resources (private topics, categories, posts, or hidden tags) were redirecting users to URLs containing the resource slug, even when the…
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user didn't have access to view the resource. This leaked potentially sensitive information (e.g., private topic titles) via the redirect Location header and the 404 page's search box. This issue is patched in versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0. No known workarounds are available.
Deeper analysisAI
CVE-2026-23743 is an information disclosure vulnerability in Discourse, an open source discussion platform. It affects versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0. Specifically, permalinks pointing to access-restricted resources—such as private topics, categories, posts, or hidden tags—redirect users without access to URLs containing the resource slug. This leaks potentially sensitive information, like private topic titles, through the redirect Location header and the 404 page's search box. The issue is classified as CWE-200 with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).
Any unauthenticated attacker with network access can exploit this vulnerability with low complexity and no user interaction. By requesting permalinks to restricted resources—through guessing, enumeration, or external referrals—attackers can extract sensitive metadata from the redirect responses or 404 pages, enabling reconnaissance of private content structures and titles that should remain hidden.
The vulnerability is patched in Discourse versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0, as detailed in the GitHub security advisory at https://github.com/discourse/discourse/security/advisories/GHSA-v5jw-rxc6-4cvv. No known workarounds are available.
Details
- CWE(s)