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CVE-2023-38691— matrix-appservice-bridge doesn't verify the sub parameter of an openId token exhange, allowing unauthorized access to provisioning APIs

Quick assessment

Affected
matrix-org matrix-appservice-bridge
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-appservice-bridge是开源的一个服务。用于Matrix通信程序的应用服务的桥接。 Matrix-appservice-bridge存在授权问题漏洞，该漏洞源于恶意Matrix服务器可以在OpenID交换中使用外部用户的MXID，从而允许攻击者在使用配置API时冒充用户。受影响的产品和版本：Matrix-appservice-bridge 4.0.0及更高版本，8.1.2之前版本，9.0.1之前版本。

CVSS 5.0 · Medium EPSS 0.47% · P38
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I. Basic Information for CVE-2023-38691

Vulnerability Information
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Vulnerability Title
matrix-appservice-bridge doesn't verify the sub parameter of an openId token exhange, allowing unauthorized access to provisioning APIs
Source: CVE Program / CVE List V5
Vulnerability Description
matrix-appservice-bridge provides an API for setting up bridges. Starting in version 4.0.0 and prior to versions 8.1.2 and 9.0.1, a malicious Matrix server can use a foreign user's MXID in an OpenID exchange, allowing a bad actor to impersonate users when using the provisioning API. The library does not check that the servername part of the `sub` parameter (containing the user's *claimed* MXID) is the the same as the servername we are talking to. A malicious actor could spin up a server on any given domain, respond with a `sub` parameter according to the user they want to act as and use the resulting token to perform provisioning requests. Versions 8.1.2 and 9.0.1 contain a patch. As a workaround, disable the provisioning API.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Matrix-appservice-bridge 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Matrix-appservice-bridge是开源的一个服务。用于Matrix通信程序的应用服务的桥接。 Matrix-appservice-bridge存在授权问题漏洞，该漏洞源于恶意Matrix服务器可以在OpenID交换中使用外部用户的MXID，从而允许攻击者在使用配置API时冒充用户。受影响的产品和版本：Matrix-appservice-bridge 4.0.0及更高版本，8.1.2之前版本，9.0.1之前版本。
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 matrix-appservice-bridge >= 4.0.0, < 8.1.2 -

II. Public POCs for CVE-2023-38691

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III. Intelligence Information for CVE-2023-38691

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Patches & Fixes for CVE-2023-38691 (1)

Vendor Advisories for CVE-2023-38691 (1)

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

CVE-2023-38686 9.3 CRITICAL Sydent does not verify email server certificates
CVE-2023-38690 5.8 MEDIUM matrix-appservice-irc IRC command injection via admin commands containing newlines
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: matrix-appservice-bridge
Same vendor: matrix-org
Same weakness: CWE-287

V. Comments for CVE-2023-38691

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