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CVE-2021-29471— Denial of service in Matrix Synapse

Quick assessment

Affected
matrix-org synapse
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

synapse是一个应用程序。用于开放式联合即时消息和VoIP Synapse 1.33.2版本之前存在安全特征问题漏洞。该漏洞远程程序在处理中等长度的事件时导致拒绝服务。

CVSS 3.7 · Low EPSS 1.65% · P76

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2021-29471

Vulnerability Information
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Vulnerability Title
Denial of service in Matrix Synapse
Source: CVE Program / CVE List V5
Vulnerability Description
Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.33.2 "Push rules" can specify conditions under which they will match, including `event_match`, which matches event content against a pattern including wildcards. Certain patterns can cause very poor performance in the matching engine, leading to a denial-of-service when processing moderate length events. The issue is patched in version 1.33.2. A potential workaround might be to prevent users from making custom push rules, by blocking such requests at a reverse-proxy.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
synapse 安全特征问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
synapse是一个应用程序。用于开放式联合即时消息和VoIP Synapse 1.33.2版本之前存在安全特征问题漏洞。该漏洞远程程序在处理中等长度的事件时导致拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
matrix-org synapse < 1.33.2 -

II. Public POCs for CVE-2021-29471

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III. Intelligence Information for CVE-2021-29471

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Patches & Fixes for CVE-2021-29471 (1)

Vendor Advisories for CVE-2021-29471 (1)

Mailing List Discussions for CVE-2021-29471 (1)

Other References for CVE-2021-29471 (1)

IV. Related Vulnerabilities

Same product: synapse
Same vendor: matrix-org
Same weakness: CWE-400

V. Comments for CVE-2021-29471

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