SB2021083112 - Multiple vulnerabilities in Discourse

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Main Vulnerability Database SB2021083112

SB2021083112 - Multiple vulnerabilities in Discourse

Published: August 31, 2021 Updated: July 1, 2026

Security Bulletin ID SB2021083112
CSH Severity
Low
Patch available
YES
Number of vulnerabilities 6
Exploitation vector Remote access
Highest impact Information disclosure

Breakdown by Severity

Medium 33% Low 67%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 6 vulnerabilities.


1) Cross-site scripting (CVE-ID: CVE-2021-39161)

CWE-ID: CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Clear


The disclosed vulnerability allows a remote attacker to perform cross-site scripting (XSS) attacks.

The vulnerability exists due to insufficient sanitization of user-supplied data in the category name field. A remote authenticated attacker can trick the victim to follow a specially crafted link and execute arbitrary HTML and script code in user's browser in context of vulnerable website.

Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform phishing and drive-by-download attacks.


2) SQL injection (CVE-ID: CVE-2021-32784)

CWE-ID: CWE-89 - Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green


The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to SQL injection in top topics RSS feed route when handling top route parameters. A remote attacker can send a specially crafted request to disclose sensitive information.


3) Cross-site scripting (CVE-ID: CVE-2021-37633)

CWE-ID: CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Green


The vulnerability allows a remote attacker to execute arbitrary script in a victim's browser.

The vulnerability exists due to cross-site scripting in d-popover and d-html-popover attribute rendering when rendering tooltip content. A remote attacker can supply crafted content to execute arbitrary script in a victim's browser.

This vulnerability only affects sites that have modified or disabled the default Content Security Policy.


4) Improper access control (CVE-ID: CVE-2021-37693)

CWE-ID: CWE-284 - Improper Access Control

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear


The vulnerability allows a remote user to reset passwords.

The vulnerability exists due to improper access control in email token handling when reusing an unused token generated for an additional email address. A remote user can use a previously generated email token in another context to reset passwords.

Exploitation requires access to an existing account and a previously generated unused email verification token.


5) Information disclosure (CVE-ID: CVE-2021-37703)

CWE-ID: CWE-200 - Exposure of sensitive information to an unauthorized actor

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear


The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to exposure of sensitive information in the unread state message handling when processing server-published unread state messages. A remote attacker can trigger a victim client to receive a message that exposes a user's read state to disclose sensitive information.

User interaction is required.


6) Cross-site scripting (CVE-ID: CVE-2021-41095)

CWE-ID: CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Clear


The vulnerability allows a remote user to execute arbitrary script code in a victim's browser.

The vulnerability exists due to cross-site scripting in error message rendering when displaying blocked watched words containing user input. A remote user can submit crafted input to execute arbitrary script code in a victim's browser.

This only affects sites that have blocked watched words containing HTML tags and have modified or disabled the default Content Security Policy.


Remediation

Install update from vendor's website.

References