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CVE-2023-38686— Sydent does not verify email server certificates

Quick assessment

Affected
matrix-org sydent
Exploitation
Public or AI PoC available; prioritize validation
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基金会的一款Matrix身份验证服务器API的实现。 Sydent 2.5.6之前版本存在信任管理问题漏洞，该漏洞源于允许拥有网络特权访问权限的攻击者拦截Sydent的电子邮件。

CVSS 9.3 · Critical EPSS 0.27% · P17

Possible ATT&CK Techniques 1 AI

T1071 · Application Layer Protocol
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I. Basic Information for CVE-2023-38686

Vulnerability Information
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Vulnerability Title
Sydent does not verify email server certificates
Source: CVE Program / CVE List V5
Vulnerability Description
Sydent is an identity server for the Matrix communications protocol. Prior to version 2.5.6, if configured to send emails using TLS, Sydent does not verify SMTP servers' certificates. This makes Sydent's emails vulnerable to interception via a man-in-the-middle (MITM) attack. Attackers with privileged access to the network can intercept room invitations and address confirmation emails. This is patched in Sydent 2.5.6. When patching, make sure that Sydent trusts the certificate of the server it is connecting to. This should happen automatically when using properly issued certificates. Those who use self-signed certificates should make sure to copy their Certification Authority certificate, or their self signed certificate if using only one, to the trust store of your operating system. As a workaround, one can ensure Sydent's emails fail to send by setting the configured SMTP server to a loopback or non-routable address under one's control which does not have a listening SMTP server.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Matrix Sydent 信任管理问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Matrix Sydent是英国Matrix基金会的一款Matrix身份验证服务器API的实现。 Sydent 2.5.6之前版本存在信任管理问题漏洞，该漏洞源于允许拥有网络特权访问权限的攻击者拦截Sydent的电子邮件。
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 < 2.5.6 -

II. Public POCs for CVE-2023-38686

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 10406 chars
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III. Intelligence Information for CVE-2023-38686

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Patches & Fixes for CVE-2023-38686 (2)

Vendor Advisories for CVE-2023-38686 (1)

Other References for CVE-2023-38686 (4)

Same Patch Batch · matrix-org · 2023-08-04 · 4 CVEs total

CVE-2023-38690 5.8 MEDIUM matrix-appservice-irc IRC command injection via admin commands containing newlines
CVE-2023-38691 5.0 MEDIUM matrix-appservice-bridge doesn't verify the sub parameter of an openId token exhange, allo
CVE-2023-38700 3.5 LOW matrix-appservice-irc events can be crafted to leak parts of targeted messages from other

IV. Related Vulnerabilities

Same product: sydent
Same vendor: matrix-org
Same weakness: CWE-295

V. Comments for CVE-2023-38686

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