What is the CVSS score of CVE-2021-41163?

CVE-2021-41163 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 19.8%.

Is there a patch available for CVE-2021-41163?

Yes, a patch is available for CVE-2021-41163. Update the affected software to the latest version immediately.

Discourse CVE-2021-41163

CRITICAL

Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') (CWE-74)

2021-10-20 security-advisories@github.com

RCE Discourse

9.8

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-74 OWASP Top 10:2025 A05:2025 - Injection ASVS 5.0 V1 - Encoding and Sanitization Input neutralization, injection prevention
Impact	CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required.
Exploit ScenarioDerived	This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the critical-severity affected system.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.

Patch available 19.8% exploitation probability (EPSS)

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AnalysisAI

Discourse is an open source platform for community discussion. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified under CWE-74. Discourse is an open source platform for community discussion. In affected versions maliciously crafted requests could lead to remote code execution. This resulted from a lack of validation in subscribe_url values. This issue is patched in the latest stable, beta and tests-passed versions of Discourse. To workaround the issue without updating, requests with a path starting /webhooks/aws path could be blocked at an upstream proxy. Affected products include: Discourse.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.8 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionNVD

Discourse is an open source platform for community discussion. In affected versions maliciously crafted requests could lead to remote code execution. This resulted from a lack of validation in subscribe_url values. This issue is patched in the latest stable, beta and tests-passed versions of Discourse. To workaround the issue without updating, requests with a path starting /webhooks/aws path could be blocked at an upstream proxy.

Threat Intelligence Overview

EPSS Score

19.8%

Top 3% exploitable

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity CRITICAL

CISA KEV No

Public POC No

EPSS 19.8%

Patch available Yes

Active threat No

Deciding rule

CRITICAL severity

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +20

CVSS: +49

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Affected Products (CPE)NVD

cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*

cpe:2.3:a:discourse:discourse:2.8.0:beta1:*:*:*:*:*:*

cpe:2.3:a:discourse:discourse:2.8.0:beta2:*:*:*:*:*:*

cpe:2.3:a:discourse:discourse:2.8.0:beta3:*:*:*:*:*:*

cpe:2.3:a:discourse:discourse:2.8.0:beta4:*:*:*:*:*:*

cpe:2.3:a:discourse:discourse:2.8.0:beta5:*:*:*:*:*:*

cpe:2.3:a:discourse:discourse:2.8.0:beta6:*:*:*:*:*:*

More in Discourse

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CVE-2025-48954 HIGH Act Now POC

8.1 Jun 25

Discourse versions prior to 3.5.0.beta6 contain a reflected cross-site scripting (XSS) vulnerability in social login fun

CVE-2022-46162 CRITICAL Act Now POC

9.8 Nov 30

discourse-bbcode is the official BBCode plugin for Discourse. Rated critical severity (CVSS 9.8), this vulnerability is

CVE-2026-27934 HIGH This Week POC

8.7 Mar 19

Unauthorized information disclosure in Discourse discussion platform versions prior to 2026.3.0-latest.1, 2026.2.1, and

CVE-2024-47773 HIGH This Week POC

8.2 Oct 08

Discourse is an open source platform for community discussion. Rated high severity (CVSS 8.2), this vulnerability is rem

CVE-2026-26265 HIGH This Week POC

7.5 Feb 26

Discourse versions prior to 2025.12.2, 2026.1.1, and 2026.2.0 contain an insecure direct object reference (IDOR) in the

CVE-2021-3138 HIGH This Week POC

7.5 Jan 14

In Discourse 2.7.0 through beta1, a rate-limit bypass leads to a bypass of the 2FA requirement for certain forms. Rated

CVE-2026-26077 MEDIUM This Month POC

6.5 Feb 26

Unauthenticated attackers can submit forged webhook payloads to multiple email provider integrations in Discourse versio

CVE-2023-38706 MEDIUM This Month POC

6.5 Sep 15

Discourse is an open-source discussion platform. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploi

CVE-2024-53991 MEDIUM This Month POC

5.9 Dec 19

Discourse is an open source platform for community discussion. Rated medium severity (CVSS 5.9), this vulnerability is r

CVE-2025-48877 CRITICAL Act Now

9.8 Jun 09

Discourse versions prior to 3.4.4 (stable), 3.5.0.beta5 (beta), and 3.5.0.beta6-dev (tests-passed) contain a critical vu

CVE-2023-47121 CRITICAL Act Now

9.8 Nov 10

Discourse is an open source platform for community discussion. Rated critical severity (CVSS 9.8), this vulnerability is

CVE-2022-39355 CRITICAL Act Now

9.8 Oct 26

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Same weakness CWE-74 – Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

View all

CVE-2019-2725 CRITICAL POC

9.8

CVE-2013-2251 CRITICAL POC

9.8

CVE-2022-27924 HIGH POC

7.5

CVE-2016-4010 CRITICAL POC

9.8

CVE-2015-1592 HIGH POC

7.5

CVE-2025-20281 CRITICAL POC

10.0

CVE-2023-29525 HIGH POC

8.8

CVE-2015-7309 MEDIUM POC

6.5

Same technique RCE

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CVE-2021-44228 CRITICAL POC

10.0

CVE-2017-7269 CRITICAL POC

9.8

CVE-2022-47966 CRITICAL POC

9.8

CVE-2012-4681 CRITICAL POC

9.8

CVE-2023-3519 CRITICAL POC

9.8

CVE-2015-5119 CRITICAL POC

9.8

CVE-2016-4117 CRITICAL POC

9.8

CVE-2015-3113 CRITICAL POC

9.8

References

Advisories & patches

PATCH https://github.com/discourse/discourse/commit/fa3c46cf079d28b086fe1025349bb00223a5d5e9 REF https://github.com/discourse/discourse/security/advisories/GHSA-jcjx-pvpc-qgwq

Search Externally

GitHub PoC

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