CVE-2026-26973 (GCVE-0-2026-26973)
Vulnerability from cvelistv5 – Published: 2026-02-26 19:19 – Updated: 2026-02-26 20:41
VLAI
EPSS
VEX
Title
Discourse doesn't scope reviewable notes to user-visible reviewables
Summary
Discourse is an open source discussion platform. Versions prior to 2025.12.2, 2026.1.1, and 2026.2.0 have an IDOR (Insecure Direct Object Reference) in `ReviewableNotesController`. When `enable_category_group_moderation` is enabled, a user belonging to a category moderation group can create or delete their own notes on **any** reviewable in the system, including reviewables in categories they do not moderate. The controller used an unscoped `Reviewable.find` and the `ensure_can_see` guard only checked whether the user could access the review queue in general, not whether they could access the specific reviewable. Only instances with `enable_category_group_moderation` enabled are affected. Staff users (admins/moderators) are not impacted as they already have access to all reviewables. The issue is patched in versions 2025.12.2, 2026.1.1, and 2026.2.0 by scoping the reviewable lookup through `Reviewable.viewable_by(current_user)`. As a workaround, disable the `enable_category_group_moderation` site setting. This removes the attack surface as only staff users will have access to the review queue.
Severity
4.3 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-02-26 20:40 UTC
CWE
- CWE-863 - Incorrect Authorization
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://github.com/discourse/discourse/security/a… | x_refsource_CONFIRM |
Impacted products
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"nvd": "{\"cve\":{\"id\":\"CVE-2026-26973\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-02-26T20:31:37.327\",\"lastModified\":\"2026-06-17T10:26:28.087\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Discourse is an open source discussion platform. Versions prior to 2025.12.2, 2026.1.1, and 2026.2.0 have an IDOR (Insecure Direct Object Reference) in `ReviewableNotesController`. When `enable_category_group_moderation` is enabled, a user belonging to a category moderation group can create or delete their own notes on **any** reviewable in the system, including reviewables in categories they do not moderate. The controller used an unscoped `Reviewable.find` and the `ensure_can_see` guard only checked whether the user could access the review queue in general, not whether they could access the specific reviewable. Only instances with `enable_category_group_moderation` enabled are affected. Staff users (admins/moderators) are not impacted as they already have access to all reviewables. The issue is patched in versions 2025.12.2, 2026.1.1, and 2026.2.0 by scoping the reviewable lookup through `Reviewable.viewable_by(current_user)`. As a workaround, disable the `enable_category_group_moderation` site setting. This removes the attack surface as only staff users will have access to the review queue.\"},{\"lang\":\"es\",\"value\":\"Discourse es una plataforma de discusi\u00f3n de c\u00f3digo abierto. Versiones anteriores a 2025.12.2, 2026.1.1 y 2026.2.0 tienen una IDOR (Referencia Directa Insegura a Objeto) en `ReviewableNotesController`. Cuando `enable_category_group_moderation` est\u00e1 habilitado, un usuario que pertenece a un grupo de moderaci\u00f3n de categor\u00eda puede crear o eliminar sus propias notas en cualquier elemento revisable del sistema, incluyendo elementos revisables en categor\u00edas que no modera. El controlador us\u00f3 un `Reviewable.find` sin \u00e1mbito y la protecci\u00f3n `ensure_can_see` solo verificaba si el usuario pod\u00eda acceder a la cola de revisi\u00f3n en general, no si pod\u00eda acceder al elemento revisable espec\u00edfico. Solo las instancias con `enable_category_group_moderation` habilitado se ven afectadas. Los usuarios del personal (administradores/moderadores) no se ven afectados ya que ya tienen acceso a todos los elementos revisables. El problema est\u00e1 parcheado en las versiones 2025.12.2, 2026.1.1 y 2026.2.0 al limitar la b\u00fasqueda de elementos revisables a trav\u00e9s de `Reviewable.viewable_by(current_user)`. Como soluci\u00f3n alternativa, deshabilite la configuraci\u00f3n del sitio `enable_category_group_moderation`. 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"redhat_vex": {
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"source": "Red Hat CSAF VEX",
"status": "final",
"title": "Discourse doesn\u0027t scope reviewable notes to user-visible reviewables",
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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.
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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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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