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CVE-2021-29431— SSRF in Sydent due to missing validation of hostnames

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 存在安全漏洞，该漏洞源于缺乏参数验证或IP地址黑名单，可能导致Sydent向内部系统发送HTTP GET请求。

CVSS 7.7 · High EPSS 1.19% · P67
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I. Basic Information for CVE-2021-29431

Vulnerability Information
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Vulnerability Title
SSRF in Sydent due to missing validation of hostnames
Source: CVE Program / CVE List V5
Vulnerability Description
Sydent is a reference Matrix identity server. Sydent can be induced to send HTTP GET requests to internal systems, due to lack of parameter validation or IP address blacklisting. It is not possible to exfiltrate data or control request headers, but it might be possible to use the attack to perform an internal port enumeration. This issue has been addressed in in 9e57334, 8936925, 3d531ed, 0f00412. A potential workaround would be to use a firewall to ensure that Sydent cannot reach internal HTTP resources.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
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 代码问题漏洞
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 存在安全漏洞，该漏洞源于缺乏参数验证或IP地址黑名单，可能导致Sydent向内部系统发送HTTP GET请求。
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-2021-29431

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III. Intelligence Information for CVE-2021-29431

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Patches & Fixes for CVE-2021-29431 (3)

Vendor Advisories for CVE-2021-29431 (1)

Other References for CVE-2021-29431 (2)

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

CVE-2021-29430 7.5 HIGH Denial of service attack via memory exhaustion
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-2021-29431

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