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CVE-2021-29430— Denial of service attack via memory exhaustion

Quick assessment

Affected
matrix-org sydent
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.

Matrix Sydent是英国Matrix.org基金会的一款Matrix身份验证服务器API的实现。 Sydent 存在资源管理错误漏洞，该漏洞导致内存耗尽和拒绝服务。

CVSS 7.5 · High EPSS 1.83% · P78
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I. Basic Information for CVE-2021-29430

Vulnerability Information
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Vulnerability Title
Denial of service attack via memory exhaustion
Source: CVE Program / CVE List V5
Vulnerability Description
Sydent is a reference Matrix identity server. Sydent does not limit the size of requests it receives from HTTP clients. A malicious user could send an HTTP request with a very large body, leading to memory exhaustion and denial of service. Sydent also does not limit response size for requests it makes to remote Matrix homeservers. A malicious homeserver could return a very large response, again leading to memory exhaustion and denial of service. This affects any server which accepts registration requests from untrusted clients. This issue has been patched by releases 89071a1, 0523511, f56eee3. As a workaround request sizes can be limited in an HTTP reverse-proxy. There are no known workarounds for the problem with overlarge responses.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Matrix Sydent 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Matrix Sydent是英国Matrix.org基金会的一款Matrix身份验证服务器API的实现。 Sydent 存在资源管理错误漏洞，该漏洞导致内存耗尽和拒绝服务。
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 sydent < 2.3.0 -

II. Public POCs for CVE-2021-29430

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III. Intelligence Information for CVE-2021-29430

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Patches & Fixes for CVE-2021-29430 (3)

Vendor Advisories for CVE-2021-29430 (1)

Other References for CVE-2021-29430 (2)

Same Patch Batch · matrix-org · 2021-04-15 · 4 CVEs total

CVE-2021-29431 7.7 HIGH SSRF in Sydent due to missing validation of hostnames
CVE-2021-29432 5.3 MEDIUM Malicious users could control the content of invitation emails
CVE-2021-29433 4.3 MEDIUM Denial of service (via resource exhaustion) due to improper input validation

IV. Related Vulnerabilities

Same product: sydent
Same vendor: matrix-org
Same weakness: CWE-20

V. Comments for CVE-2021-29430

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